Anecdata, but another case here. I wear them approx. 6 months per year because of knocking heating sounds. Anyway, doctor recommended to do ear cleansing once a year and it helped, maybe 80% of the ringing sound is gone. Earplugs caused all the grease to end up compressed and deep in the ear canal. After a while it blocked signal transmission through the auditory nerve enough so that my brain thinks there's no audio input and it starts compensating with these imaginary ringing sounds.

Earplugs can give you tinnitus because they provide almost complete silence, in which your brain can latch on to the tinniest pre-existing tinnitus sound that was already there (which is pretty common in the current era of hearing-damaging equipment and environments), but you didn't notice it before. Once the brain notices it, it's basically impossible to unhear it. That's my theory at least.

I've done pretty much everything I could imagine to try to identify the root cause, no doctor could give a reasonable diagnosis. My tinnitus started after a night with earplugs, but it could have been a coincidence since I also used noise-cancelled Sony headphones. Who knows ¯\_(ツ)_/¯