Closing issues with commit message

Hi

I'm still trying to close mantis issues by committing changes
with a matching "Fixed" message. The changeset is imported
but the issue is not closed.

This is the "Resolved Issues references RegEx (Pass 1)":
/\bfix(?:ed|es|)\s+(?:bug|issue)?\s*#(\d+)/i

The commit message starts with:
"! Fix #2252: Bla bla."

Checking with https://regex101.com/ The regex does match
the commit message. The changeset is added as "Related
Changesets" to issue 2252, with "Affected Issues 2252".
But it is still open. Where can I look to see what's going
on, why this issue (and any other) is not closed?

Thanks

bye  Fabi