I have checked ignitor for continuity and all is good there. It does light up and then slowly dim in about 30 seconds with no flame starting. Gas valve solenoids are also good. Thermal fuse is good.

My thoughts so far are the entire gas valve assembly, but I have no idea how to test that without just buying a brand new one and putting it in. Before I order an assembly, how do I test the old one or are there any more suggestions?