
Same for me. iPad Pro 2020, using Chrome app. It worked a couple days ago. Now it’s the same, loop on Loading screen.
Have you tried to see if you can load any other games? It might be an issue with the game itself, such as a map with an extraordinarily high number of tokens or complex lighting. You might be able to load on a different page if your gm can change the player flag to a different map, preferably one without a custom audio (jus in case). I just loaded a game sitting page to a map that's about 232x172 squares, so the size is not likely to be an issue.
If you are not able to connect to another game, and switching the player flag doesn't help, you should file a Help Center Request.
As an aside, Chrome and Firefox on iOS are actually Safari with an interface overlay, not the actual browsers, so one is likely to give the same general performance as another.
Have you tried switching the player flag? (You may need to use a Dummy Account). If the Dummy Account cannot log in either, and loading in a private browsing window also fails, you should file a Help Center Request.