ENQUEUE functions could not be generated

What causes this issue?

When activating lock objects, function modules are generated for
setting (ENQUEUE_<lock object name>) and unsetting (DEQUEUE_<lock
object name>) locks.
An error occurred when generating these function modules.

System Response

The lock object is not activated.

How to fix this error?

Try the activation again. Check whether one of the function modules to
be generated is locked by another user. If the lock was not correctly
removed due to a system failure, for example, you can unlock manually.

Error message extract from SAP system. Copyright SAP SE.