I have tried several hdmi cables including 2 brand new.
I just downloaded the new retropie 3.6 on Sunday so I believe everything is up to date.
In the config file I had to change the hdmi drive, group, mode, set the screen resolution and then use the options to not use a few pixels so it wouldn’t over run the screen.
The link below is what I followed.
https://www.raspberrypi.org/forums/viewtopic.php?f=78&t=103773