tnt does not blow up with flint and steel in nether

I was going to blow up tnt in the nether to try and find netherite. I used flint and steel to blow the tnt. It did not work so I used a bed and then the tnt blew up after the bed blew up.(like when tnt blows up other tnt) When I went back to the overworld to find diamonds to repair my gear the tnt blew up with flint and steel. (tnt explodes was on) the first time i tried to light it the topof the block was set on fire. I tried again and it was lit on fire again. It could be because of lag beacuse my kindle is laggy. Kinda like to much lag delays when damage is done