Requests cannot be released during the upgrade

What causes this issue?

An upgrade to a new version is currently running in your SAP ystem. No
change requests or transports are released in the current upgrade phase.

System Response

Request &V1& is not released.

How to fix this error?

Wait for the upgrade to finish. You can then release request &V1&.
Further information can be found in the upgrade guide.
Note in particular the section about adjusting the ABAP Dictionary
objects.

Error message extract from SAP system. Copyright SAP SE.