The only problem I had with Plastiq on a recent payment attempt was that their two-factor authentication was broken for a while.

Over the phone for a while they kept giving me the same 6-digit verification code ever time I re-asked for it, and every time I entered it, the website said "verification code invalid".

I notified them of my login problems, it said online that they would reply within 24 hours, but they wrote back pretty quickly saying that they had "reset" something about my account (in addition to other suggestions).

Well, no wonder that initial 6-digit code was invalid. Because when I tried again after they emailed me, it gave me a 7-digit verification code, and that worked immediately.

I wrote back to them to explain to them that the number of digits in the original code it was giving me seems to have been the problem.