Update... I've tried the methods that worked in Crystal's post:
Incorrect Response from Alexa Testing
They have not helped at all. Moreover, if I type an utterance now, it won't show up in the testing history panel. Instead, alongside the error Crystal was receiving, I am also receiving the message @Sam1121 had/has. I don't know if yours has started working properly again? (sorry for the mention)
I've read everything I can about this issue and nothing is helping. My blocks aren't complicated, I just have many intents, which all look similar to this:
Each has around 20 possible utterances, none of which are working right now. I'm tearing my hair out 
(figuratively)
Please help.