Hello Computers1,
Thank you for posting in Microsoft Community forum.
Based on the description, you mean different users sign in the same machine, one user can use windows search, but the other one cannot use, so maybe the user policy control the setting.
Are the machines and users in the domain? If so, you can try to export the gpresult for different users and compare the result.
Sign in the working user.
For checking User Configurations within gpresult, we can follow steps below.
Logon the machine using normal domain user account.
Create a folder named F1.
Open CMD (do not run as Administrator).
Type gpresult /h C:\F1\gpo.html and click Enter.
Open gpo.html and check gpo setting under "User Details".
Sign in the non-working user.
For checking User Configurations within gpresult, we can follow steps below.
Logon the machine using normal domain user account.
Create a folder named F2.
Open CMD (do not run as Administrator).
Type gpresult /h C:\F2\gpo.html and click Enter.
Open gpo.html and check gpo setting under "User Details".
You can also check the registry between working user and non-working user.
If the registry is below.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Search] "SearchboxTaskbarMode"=dword:00000000
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Search] "SearchboxTaskbarMode"=dword:00000001
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Search] "SearchboxTaskbarMode"=dword:00000002
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Search] "SearchboxTaskbarMode"=dword:00000003
Reference
Add or Remove Search Button on Taskbar in Windows 11 Tutorial | Windows 11 Forum (elevenforum.com)
I hope the information above is helpful.
Best Regards,
Daisy Zhou