Hi,
Thanks for posting your question in the Microsoft Q&A forum.
First I need to clarify that MS To Do is enabled if it is assigned correct license:
Based on your description, I have a couple questions as below:
- Do any of your users have Windows? Are they also having this problem? Did the same issue occur with Outlook for Windows?
- "couple of Outlook for Mac users have reported that they cannot access the MS To Do feature" did all Outlook for Mac have this problem? If not, please let the issue users test with other Mac which works with no error.
If yes, I suspect that this is known issue, because Microsoft To-Do and Outlook for Mac aren't fully integrated , we suggest you try to use Microsoft To-Do App on Mac: Microsoft To-Do for Mac is here!