Hello Answermesoon (I hope this is soon enough .... ),

Weird, that clicking on "About Firefox" doesn't work ....

Would you please try this :

Type in the address bar about:preferences and press Enter

Scroll down to "Firefox Updates" and click on 'Check for updates".

Does that work  ?

That worked thank you and the original method now works as well. This is the second time that I have had this problem in last year?

Answermesoon said

That worked thank you and the original method now works as well. This is the second time that I have had this problem in last year?

I'm glad it works now  ! I haven't a clue why clicking on "About Firefox" wouldn't work before ......