Hi @Chris Bechtel ,
I've attempted this with my credentials and it saves just fine when logging out and back in. It seems to be isolated to this single user.
I tried to test in my lab tenant and the signature can save successfully as well, so, agree with you that it's likely to be a issue with the particular user. In order to help narrow down the issue, I am wondering were you using the same browser on the same computer as the problematic user when did the test with your own credentials?
Besides, it's suggested to let the user try using different browsers or opening the browser in private mode to see the result.
You can also have a look at the Service Health page in the Microsoft 365 Admin Center to check if there's any potentially relevant known issues in your tenant.
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