Unable to install OS update on my MacBook Pro with error "Search for update failed"?

The machine you have listed does qualifies for Sonoma

macOS Sonoma is compatible with these computers

That said there is a Manual Way around this

I would try this Terminal Command which will only Search for ALL Qualifying Full Versions of macOS for this computer

softwareupdate --list-full-installers

Hit return key

If it finds Sonoma 14.5, the current version, you are good to go with the Next Terminal Command

softwareupdate --fetch-full-installer --full-installer-version 14.5

Again, Return Key

It will Only Download the Full Version ( 12.xx GB )

It will place a new Application in Applications folder called " Install Sonoma Application "

It Does Not Auto Launch

Ready to go and have done a TM Backups ?

Launch it like another application

Be Sure to have an Active and Functional Internet Connection during the above process

It is a Requirement , to have successful installation

Sorry the whole Physical Drive will have Containers and within the Containers will be Volumes

The Volume being referenced MacIntosh HD - Data is actually your User Data

Again, if the Operating System Monterey 12.3 was on the KINGSTON SNVS2000G 2.00 TB (Solid State - TRIM: Yes)  that seems to be where the issue is.

First thing - Restart the Access Point / Router and try again

Software on the computer interfering with the download process including AntiVirus Software

Notation: Disabling the AV Software may or may not solve the issue. Removal of the AV Software may increase the chances of the download to perform as expected.

Running behind a VPN which may increase Packet losses or corruption of the download 

Restart in Safe Mode. This will perform a Disk Repair, clear cache files and only load Apple Software, extensions and fonts. The boot up will be slow and can take some time - Normal and Try Again using the Software Update Applet in System Preferences

Worst case - Restart in Recovery Mode and choose Reinstall macOS. This in theory will pull the latest version of Sonoma available and commence the installation.

Thank you for that significant information

This does change this a great deal

Booting Monterey 12.3 from this drive should not be an issue.

Nor should updating to current version macOS Monterey 12.7.5 for upgrading all the way to Sonoma 14.5

disk1 - APPLE SSD AP2048N 2.00 TB (Solid State - TRIM: Yes) 

One reason why things are not progressing as expected would because the Apple SSD AP2048N may be failing

This would be supported by the below finding from Etrecheck report

There has bee, yet another suggestion, by another Contributor @MrHoffman

" run DriveDx " which would check the Health of the 2 TB Drive

Have held off making that suggestion only because I have Zero Experience in using this application and even less abilities to understand the Report it will generate

Runtime: 7:16

Performance: Below Average

Thank you and Thank you my fellow Colleague @BDAqua

At this point, I concur with @BDAqua suggestion to start Over from Scratch

Depending on that outcome, hopefully successfully installing Monterey 12.7.5

This machine does report having a T2 Controller

Should something in the T2 Controller has become corrupted

As a Last Resort

How to revive or restore Mac firmware

Rarely, a Mac with Apple silicon or the Apple T2 Security Chip might stop responding and need to be revived or restored by another Mac.

Labyrinth67 wrote:

Its actually running 12.3 build version: 21E230

Sorry, that was my fault...

No problems there 👍

So many details and numbers to remember, it does happen to myself sometimes

The update of Monterey 12.3 was released March 14, 2022

I am surprised the Software Update applet has not altered you to various Monterey Updates

The current Monterey has since reached Monterey 12.7.5 Released May 13, 2024

That said, something seems very amiss on this machine

To get a better idea of possibly were this issue is occurring

Download the Application Etrecheck ( External Link ) directly from the Developer.

The Application is Not a " Silver Bullet " but only a tool to examine the Hardware / Software used on this computer 

This is a Diagnostic Tool that makes no changes to the computer.

It makes a coherent and readable inventory of both the Hardware and Software used on the computer 

The application is free or paid for added features. 

The Report will Not Reveal Any Personal Information. 

Post back the Full Report - copy and paste - >>>> using the Additional Text Icon  <<<<

Can you please clarify" Running OS 12.13 " of macOS Monterey

Better still, in terminal copy and past this command

 sw_vers

The post back the exact output of the command

I ask as my records to not match with OS 12.13

It is possible this could be the source of all the problems

Q - Runtime: 7:16

Q - Performance: Below Average

Q - Low performance - EtreCheck report took an unusually long time to run.

A - The above three items are not a good sign, especially on such a Powerful Computer.

Q- Mac Pro (2019)

Q - Mac Pro Model: MacPro7,1

Q - 3,2 GHz 16-Core Intel Xeon W (W-3245) CPU: 16-core

Q - 96 GB RAM - Upgradeable

A - This specific machine should just be flying without the slightest problem

Q - disk0 - KINGSTON SNVS2000G 2.00 TB (Solid State - TRIM: Yes) 

A - How recently was the Kingston SSD driven added to this configuration ?

A - In Monterey 12.3 running from this specific drive ?

A - If yes, we have seen , starting just around the time Monterey 12.3 was introduced where the Installer of the Monterey 12.3.1 and above would Refuse to install on a Non Apple Original Drive

A - The issue was the EFI Boot ROM within the Monterey 12.3.1 would detect the Non Apple Drive

A - The solution was to Flip Out the After Market Kingston SSD and replace of the Apple Original Drive

A - Install Monterey 12.3.1 to the Original Drive and in so doing, Flashing the Computer ( not the drive ) with a new Boot ROM

A - Thereafter, reverse the above and placing the Kingston Drive back into Service and run the Monterery 12.3.1 to the After Market Drive

Q - disk1 - APPLE SSD AP2048N 2.00 TB (Solid State - TRIM: Yes) 

Internal PCI-Express 8.0 GT/s x4 NVM Express

➡️ Now, I would like to introduce yet another fellow Colleague @ BDAqua who has also offered me some help with your computer issue

Both Contributors come with a long history of experience and a wealth of knowledge on may Apple Technical Issues

I mention this because this specific computer Mac Pro (2019) has some configurations I am not as familiar with as other Computer

Perhaps either or both contributor may or may not directly join your question

Have put out a call for some additional help

Hope to get back to you when that help arrives

Delete this file & restart...

/Library/LaunchAgents/com.uaudio.ua_mixer_engine.plist

Sorry. it's not clear to me so I must ask...

Did you Erase the whole drive before trying to downgrade?

I need some help here

GPT (GUID-Partitionstabelle)

Am I seeing a MS Windows Partition Map ??

Off topic

If I have offended some time recently, I do apologize