What the fuck? Has anyone had any success using their service in the past day?
I have.
tried numerous times to accelerate my transaction, straight on the hour, in the very first second of a new hour - Submissions are beyond limit. Tried 10 more times - same bullshit.
I have used their service lots of times before, and there was never an issue as long as I did it straight in the first few seconds of a new hour.
It is possible that your system clock and their system clock are not set exactly the same. So, by the time you think it is "straight on the hour", their system might have already been accepting transactions for many seconds.
I have made sure my clock is synced properly
How do you know that your clock is synced to their clock?
When I'm trying to help someone out and accelerate their transaction for them, I typically start trying to use viaBTC about 3 or 4 minute before the hour. Then I repeated try over and over until it either succeeds or until it is 3 or 4 minutes after the hour. If I miss the window of opportunity (because I'm too slow entering the captcha), then I try again the next hour. I've never had it take more than 3 hours of trying before being successful.