Hi,
Thank you for posting in Microsoft Q&A forum.
1,Please view the ConfigMgrPrereq.log CMUpdate.log and ConfigMgrAdminUISetup.log to check if the upgrade is successfully completed.
2,Please check the SmsAdminUI.log to see if there is any error about the failed Configuration Manager console activity.
3,What version of MECM you are upgraded to? Below similar thread for your reference. The solution is to install the latest .NET Framework version 4.8.
Starting in version 2303, site servers and specific site systems require Microsoft .NET Framework version 4.8. Before you run setup to install or update the site, first update .NET and restart the system.
Console fails to load after Configuration Manager 2403 upgrade
Note: This is non-Microsoft link, just for your reference.
Hope above information helps.
Best regards,
Simon
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