"Oops, something went wrong"
My wife and I signed up for a free trial through T-Mobile. She was able to go to 1 class, then received the error message. She re-entered the same credit card info, deleted and reinstalled the app, and restarted her phone without a fix. She contacted Customer Service chat and spoke with a Live Agent who briefly pushed for a paid membership. When she turned it down, she was told there would be a fix in a couple hours. That was on Friday night. Saturday, same error message. She spoke to an agent on Sunday, they said to wait another 24h. She just spoke to an agent today (Monday), told to wait another 24h.
My experience: last Friday, I made a reservation for a class on Tuesday - this was booked seconds before my wife's attempt resulted in an error. I ended up cancelling since the plan was to go together. I tried to book a class this afternoon, and received the same "Oops, something went wrong" as my wife did. My CS agent gave me "one solution" and was extremely pushy about signing up for a paid membership to fix the problem.
Coincidental pattern? Nah. This smells like a manufactured problem in order to absolve themselves of providing anything more than a few credits (out of 55 credits in the trial offer) to get people to pay for a membership.
Just wanted to throw a PSA out there if anyone else is going this route.