Thank you for posting in Microsoft Q&A forum.
To narrow down the issue, could you please share the error screenshot on our CM environment?
We could also check the upgrade process on the CM console (by navigating to Monitoring / Updates and Servicing Status, right-click your Update Name and select Show Status) Like the image shown below.
Please refer to this excellent blog for more details:
https://systemcenterdudes.com/step-by-step-sccm-2010-upgrade-guide/
Note: this is non-Microsoft article just for your reference.
Have a good day!
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