re; JAERED answer .i sympathise with your similar problem . You are probably , like me ,trying to link to ledger for extra security . Thanks for everyone elses replies / time ....i will look into your suggestions to resolve this. 
You've both tried removing the metamask extension and reinstalling it afterwards, but make sure you've archived everything important before removing the extension for reinstallation.
You are both using Chrome browser and you have followed all the suggestions people made above, but the problem still hasn't been solved for both of you. Try using metamask with another browser that doesn't share the source code with Chrome like firefox.