Showing my mail in name - cannot set alias

When I go to settings then I check “Only display alias”, then write something in Alias line - clicking apply button makes my settings return to blank, then only email line stays unchanged.
Like I’m not allowed to make any changes in Tools window. Running as admin doesn’t help, also reinstalled, same problem. Got 64-bit version, what to do? :embarassed: I don’t want others to know my mail, lol