To resolve that there are several solutions you can use, some common ones are mentioned in restore Outlook functionality this flowchart. Sometimes browsers can automatically disable some of the Outlook web features, which can lead to this issue. Follow the below given steps to enable the permissions.

Visit Firefox support to learn how to Disable or remove Add-ons. You can also Sign out manually then close all browser windows. Some users may not be able to empty their Deleted Items folder. Some customers may not be able to insert GIFs from the Insert Emojis and GIFs button. If you can't open Outlook, or Outlook disappears or crashes, one of your add-ins may be to blame or you restore Outlook functionality may need to update Outlook.

Out-of-date software and corrupted Outlook profiles are two of the most common issues that can prevent you from sending and receiving email. If you're an admin with multiple users reporting problems, you also should check for service issues with Microsoft 365. This kind of error usually indicates some issues on the disk where your Outlook PST file is located. It can be caused due to improper installation of a program, corruption in the hard drive or registry file, etc. This has nothing to do with the email client