Nether Portal Won't Light?

The standard nether portal is 4 wide x 5 high obsidian (2 wide x 3 high opening). It actually does not even matter if the corners are filled in, so it can be as few as 10 obsidian blocks total.

Is this single player or on a server (I'm not familiar with Xbox version)? In some cases a protective plugin might stop you from igniting things in a protected area (can you ignite a leaf or wood plank block?). And one (PC) server I tried (tekkit mod) had a bunch of things disabled including the nether because they thought it might be causing lag. But how would I get glowstone or blaze rods, etc. With nether (and mystcraft mod) disabled? So I found a different server with nothing disabled.

I don't think you actually can make one bigger than 4x5.

The xbox version isn't currently updated to allow portals bigger than 4x5, so you will have to hold out until the update

My portal is 4x5 nothing touching it except the ground but when I tried lighting it nothing happened

Nothing is working its the 4 by 5 and in every other world it lights