I found out working now ! Just for other people to see the solution:
I checked when my GA stopped working and noted the day.
Then logged in to my ftp server and checked the dates of the plug-in installations. Just the day after I installed the AO, I installed another plug-in called “Remove Footer Credit”. I deleted it now and instantly started to see live results in GA.
I don’t know if it is a conflict of plug-ins or just that plug-in. Maybe blamed AO for nothing :))
But thank you for your valuable time.
Now I need to find another means to remove footer credits :))