Tyre not seating

I've tried all that. The tyre just goes lower at another spot on the rim!

Guess the rims must have a odd lip. Just had another go and got it down to one small spot rather than the usual two. Gives my thumbs a rest overnight and try again in the morning. Never had a rim like this in many years of changing tyres.

if all that's tried have you checked also the vertical trueness of the wheel ? (although i can't see it making a difference)

the tire must too small or the rim tape is obstructing the rim hook ? (i also can't see this making a difference)

You could try another tyre to see if you get the same problem.
I have a spare if u need.