@Mrs. BLUE_MOUNTAINS_BEAR the supermod has had a look and I've copied their reply below. I appreciate you can't do the 1st as you don't know your password.
"I'm suspecting they haven't cleared their device properly and there is a way to test this, assuming they remember their not606 login details.
They need to go incognito, then sign-in - this will hopefully demonstrate to the user that there device has not been cleared.
My first guess would be what i have experienced with other users, that they clear their cookies butthey don't actually clear their cached, devices will not always have this checked and you will need to manually tick it.