GoPro7 Adjustment problem

It worked for me which leave a few possibilities 

1- your lens is dirty or defective

2- camera problem ( see if it works with original lens)

3 you are not doing what hajimoto suggests perhaps have a friend who is familiar with cameras do it with you.if redoing the installation leads to no improvement you will have to go to a camera repair shop for expert help.

one other possibility is you used an incorrect lens that is in now cross threaded. What is the brand and model number of lens. Remember the GoPro 56&7 have different thread than the 4and 3 the only correct 8.25 lens is this one

https://www.peauproductions.com/collections/gopro-hero-7-6-5-lenses/products/8-25mm-f-3-0-41d-hfov-16mp-br-no-distortion-hero-5-6-7

if you used another lens that probably the problem the 2 threads are similar but not compatible.