User master comparison incomplete; see long text

What causes this issue?

The user master comparison could not update all role and profile
assignments. There are two possible causes for this:
Your authorizations are insufficient.
Individual users were locked by another administrator.
For detailed problem descriptions, see the messages in the displayed
error log. In particular, pay attention to the associated long texts.

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?

If you have performed the user master comparison with transaction PFUD
or a variant of the report RHAUTUPD_NEW without the option "Display
Log", no log is displayed. In this case, you should select this option
and then repeat the user master comparison.
Once you have identified the error and corrected it, you only need to
perform the comparison again for the affected roles.

Error message extract from SAP system. Copyright SAP SE.