Hi Aldo,
Check on the following.
1. After Patch upgrade, the post installation script was run by your basis team.
2. Check whether your model is active. Re-activate your planning area after Patch upgrade.
3. Check the S&OP debugging guide https://share.sap.com/a:vlgnqt/MyAttachments/8fd3512a-f297-4dec-a262-8712aa946634/#, especially pg 8. on how to debug GUID error displayed in Excel Add-In.
It you have HANA Studio access, you can navigate to Administration-> Diagnostic Files -> (Sort by Data Modified desc) -> indexserver_....trc
Search for the GUID/error message and you will see the error in one of those lines.
Hope this helps.
Thanks,
Raghav