I had a similar issue with my previous travel trailer. I blew out the gas orifice with compressed air and it solved the problem. It dosen't take much of a restriction of the gas orifice to cause issues. I have had the same problem with the gas orifice on the fridge. Compressed air has worked every time for me.
2012 Grey Wolf 19RR
2008 Dodge 2500 CTD
Our new 5ver w/ DSI would take 5 or 6 times to light. I finally removed the burner and electrode and re-aligned the electrode to the dimensions in the manual. It now lights the first time it tries. Page 12 shows how it should be positioned. I had to tweek mine in both directions.