Configuring preferences and options in Outlook.com
I am seeing some other recent reports of a very similar issue. e.g.
https://learn.microsoft.com/en-us/answers/questions/5991870/outlook-com-not-saving-blocked-safe-sender-changes
https://learn.microsoft.com/en-us/answers/questions/5989552/couldnt-save-changes-when-unblocking-an-email
This may be a Microsoft infrastructure problem. Not one you can fix. All I can suggest (since you have already tried Microsoft Support) is just wait and see if the issue clears itself.
You can always try Chat again. You might get an agent who is more helpful?
- Logon to https://outlook.cloud.microsoft/
- From the main menu: Help -> ? Help
- {This should open the Help side panel}
- Search Help -> {Your problem} and press Enter
- Still need help? [Yes]
- If you get "We're here to help": Tell us your problem -> {Your problem, again} [Get Help]
- [Sign In] {Use any Outlook/Microsoft account}
- Choose a support option -> Chat with a support agent in your web browser