Nitrome games aren’t on Flashpoint because Nitrome is in the process of porting all of their games over to HTML5. Once they finish Square Meal, you can play it on www.nitrome.com.

There are at least three ways that I know of to play Nitrome flash games nowadays:
1. Use Supernova, a browser add-on you can get from the game's page on Nitrome.com
2. Use a flash enabled browser (e.g. Pale Moon) + an old version of the flash player
3. Use Flashpoint (the discord server has more info on how you can get it to work, since as you know Nitrome games are not in Flashpoint by default)

Some games however do not work on Flashpoint and get stuck on loading screens. I suspect this is because the game is trying to get level data from somewhere other than the main game file, but can't find anything because it's looking on your own computer. Square Meal is one of those, so to play it you'll need to go for solution #1 or #2.