My nether portal in minecraft won't light?

So I put obsidian in its correct shape so I know it's not the shape of the portal. Then I tried to light it with flint and steel and it just catches on fire. But I have heard people say it works differently on survival, but I'm on creative, and I'm on pocket edition. If that helps at all. Lol

Well I played on pc so I don't know if it fully solves your problem… Anyways, make sure you make the portal as 5x4 that is 5 blocks on the side and 4 blocks on the base. Then use fint and steel to light it up, when the portal's inside begins to glow stand at the portal and wait for you to warp.

You can't go to the nether on pocket editions

It's because you can't go to The Nether on pocket edition.