A cloud-based service included in Microsoft 365, delivering scalable messaging and collaboration features with simplified management and automatic updates.
Great to know that the issue has already been resolved and thanks for sharing the solution so that others experiencing the same thing can easily reference this! Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others", I'll repost your solution in case you'd like to "Accept" the answer : )
Issue Symptom:
The new created Room mailbox didn't show in Room finder.
Resolution:
A special character that was not displayed correctly in the mail address during the automated creation of the distribution group caused the error. A new attempt without special characters resulted in the rooms being displayed correctly.