Hello, @Georgieva, Nora,
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(https://docs.microsoft.com/en-us/answers/support/accepted-answers#why-only-one-accepted-answer)", I'll repost your solution in case you'd like to "Accept (https://learn.microsoft.com/en-us/answers/support/accept-answer#accepted-answer-in-a-question-thread)" the answer).
Issue Symptom:
The author wanted to know how to become the owner of a mailbox PDL to add a new team member if the current owner is out of the company.
Resolution:
After troubleshooting, the author's IT support team solved his problem through company ticket. He just needed approvals from managers.
Hope you can consider accepting the answer as it could help other members of the Microsoft Q&A community who have similar questions and are looking for solutions.
Thank you for helping to improve Microsoft Q&A!
Best Wishes,
Alex Zhang