Ah, thanks for that detail! a 404 means we haven’t even processed the form OR you are submitting to a different location than you specified in your action= form parameter in your html.
Take a look at this debugging guide which talks through how to get forms working, and if you don’t find the solution, answer those last couple of questions in the post for us (please - answer here in this thread since we have your context here :)) and we’ll be happy to help troubleshoot further!