One thing that I ran into pretty quickly was there are different versions of WeChat: the chinese one and the -- in my case -- American one. When I was in China early last year I needed to get invited to properly set up my account. I absolutely was not able to use WeChat Pay which was quite frustrating tbh. Basically the American version is a striped down version where you can chat with the Chinese version, but WeChat Pay is not even an option and sending/receiving red letters is also not possible.