That happens too often! A lot of places where I try to use a really long password will silently truncate it, but different forms will truncate at different lengths, so what might work for registration might not work for login or changing the password later.

I’m always suspicious when sites cap passwords at < 32 characters, that almost always means it’s being stored in a reversesble format someplace - maybe encrypted, maybe obfuscated, or maybe not either (banks).

The sites I really trust don’t care how long your password is because their hash size is fixed. The only real length consideration might be that if a bunch of people send obnoxiously long passwords at the same time and they are using bcryprt or scrypt it might stress the server’s cpu, so they might put an upper limit to prevent that.