Exporting to mobile is a delicate process. I have been in this hell recently.
It is difficult to figure out in which state you are, what you have tried, what has worked, and what hasn't
Does it work in your mobile connected by USB and using the Remote Debug?
This is the first step. Experiment with different rendering modes "Forward+, Mobile, Compatible"
If you still have problems I would try to see if there is a particular scene the one that is giving you problems. I would create a very simple Scene and mark it as the Main one. To see if this scene renders. If so, it means the problem is in the previous Scene.
Try to see what risky elements are in the problematic Scene: shaders, big images, ... Try to add log (print()) everywhere to see if you figure out where your code is breaking in the mobile