& assignments could not be released

What causes this issue?

You want to release one or more allocation. At least one allocation
fails the checks and cannot be released.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

The allocations that are not released are still selected and can be
changed. Check whether all characteristics with the <ZH>Entry
required</> indicator have values.

Error message extract from SAP system. Copyright SAP SE.