A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
Dear Mary,
Thank you for your posting back.
According to your response, this issue is happening equally to your colleague and having the same issue with other masters. This could be due to your old and new versions being unusually compatible. I'm afraid this issue needs to be escalated by backend log collection. I recommend you contact the administrator in your tenant and let him open a support ticket to our related team to seek further help: Get support - Microsoft 365 admin | Microsoft Learn
You can try the methods mentioned by John Korchok, these experts have more experience in the field of PowerPoint.
Thank you for your time and patience.
Sincerely,
Claire | Microsoft Community Moderator