Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
I don't know how many times Tina has been told the correct answer for this problem. Tina seems to refuse to give the correct reply, I deleted those nonsense, useless, idiotic replies. And then Alex had the gall to mark a completely wrong answer as "Answer." Alex is no better.
The solution is simple. Install updates. Your version is 15 and hasn't been updated in years. You'll have to start with a fresh version of AutoUpdate.
Download a fresh copy of the current version of AutoUpdate from this link, install and then run AutoUpdate to bring your installation to current update level, then restart your Mac.