Some tyres are just a bitch, take it off, get tyre soap if you know someone with at a tyre fitting garage. I used dove extra moisturising last time, rub it round bead and rim, then reinflate it until you hear it pop on. Then check the line on the tyre all the way round make sure it's an even gap. I did one 3 or 4 times once. No rim or tyre bead damage?