I’ve noticed this issue as well, known as “UUC”, affecting a lot of traders over the past day. While it was a problem in the past, it had been fixed for a while, so it’s disappointing to see it come up again.
Hopefully, it’ll be resolved soon. If staff curious to learn more about this issue, I’ve included some dropdown posts with more details.
Trading is HEAVILY bugged, requests failing, UUC glitch prevalent
Trade was Accepted, I received their items, they didn’t receive mine