& & & was not activated ( & )

What causes this issue?

The ABAP/4 Dictionary object was not activated. This message is followed
by the error number from table T100. This message from T100 is
displayed again in plain text in the next line.

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?

Error message extract from SAP system. Copyright SAP SE.