What should I do if my non-B visa application form won't submit while applying from the UK?

Kanyarat Jitsajjapong what you posted seems to show that none of your documents were accepted, even though you uploaded them, and made it past that step. The grey box in the picture shows NO documents. That is why I say they were probably too big. Many people have been having this problem, until they made each picture smaller than 0.5k in size.