I have 3 pi 3b+ iirc and none use other than the +5v and GND wires and the ribbon to support the display.
Thanks. I will continue to test tomorrow.
I connected the screen up as the manual recommended.
Will let you know the outcome
So far the issue seems to be resolved.
Problem was the green/yellow jumper wires that were supplied with the screen and the installation instructions showed how to connect it all together.
Removed those and just supplied power jumpers to screen and all is working.
Thanks for the great support and I hope this can help somebody else down the line with the same problem.