Did you ever see if classic search found these messages? It is an important trouble-shooting step.

Yes, the messages were found with classic search.

I'm left with two observations. Maybe they are helpful:

• In your screenshots, the filter that is working has an operator of "is" and the filter that is not working has an operator of "contains". Have you tried "is" in the bad filter?
• In your screenshot of the bad filter, something is redacted in the criterion field. I suggested that you remove everything extraneous, and I believe that you did. Is something extraneous there?

Otherwise, I'm stuck. I'm sorry. Maybe someone else will offer assistance.

That was a good idea, but it led nowhere. I change the filter to "is" but is still didn't work, and another filter that also doesn't work was already set to "is."

As for the redacted content, it's just the name of the place where I work. I don't believe the issue lies with the specifics of that text (punctuation, capitalization, spaces, etc.) as I have checked it multiple times. I'd be happy to share an unredacted version if I could do so privately, but I don't suspect you'd learn much new information (other than where I work).

Is there a way to flag this question so someone else knows to join it? Thank you again for the help.

No, there is no way to flag the thread. I have asked another person to take a look. Some other people tend to review messages and might take an interest too.

Puzzling. Try changing filter to match 'any', not 'all' - Logically, this is the same, as there is only one condition. I also suggest using fewer words in the match.