Hi @Ray Waldron,
Thank you for posting in this community.
Your problem is that when you go to visit the site as guest, there is no way to assign tasks to users, is there? (If I misunderstand anything, feel free to correct me.)
I test your question in my side, and I did not have the problem you mentioned.
Since we can't reproduce your situation, we need to narrow down the problem and try some things.
1, Delete the guest and re-add the guest.
please go to member->Add members->go to Outlook. Find your site group and delete the guest and add it again. Then check if the problem still exists.
In my test the site name is G
You can follow these articles to add a guest to site:
Add and remove group members in Outlook
Guest access in Microsoft Planner
2, Please make check whether the guest is in the Microsoft 365 groups:
Here is the article about enable gust access in groups: Manage guest access in Microsoft 365 groups.
2, Please add the guest to another site and see if the problem persists.
3, Please try adding this guest again in a different browser and see if the problem persists.
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