Hi Peter,
Thanks for reaching out in the Community. I hope you're doing great, in spite of the issues you're experiencing in PowerPoint. Let's sort this out.
I would suggest that you start
PowerPoint in safe mode,
and see if there are add-ins that might be causing this.
If the issue also occurs in safe mode, try
repairing PowerPoint. If the issue
still persists after repairing PowerPoint, I highly recommend that you reinstall
Office. There's a possibility that there are corrupted system files that's hindering PowerPoint to work properly.
To notify me and have me get back to you, simply reply to this post.