We have come across a couple of cases where iPhone users are unable to choose a password when signing up a new account. The cursor will not show up in the password field.
This has to do with some apple security settings as part of a recent update.
More information can be found here:
The way to fix this is to switch to Private in Safari, and then reopen the link:
You can then exit private mode the same way.
After this process, logins should work.
It is only new password fields that seem to be affected.