User register and login functions are called from hook_form_alter, but user isn't logged in
If a redirect is happening after print('x') then it will be lost. dmp() should show up however I prefer using Devel Debug Log in these instances so you know if then code is running then it will output to the log.

You can use the function ddl('log message') or ddl($array) and then check the report of what has been output once your code has run.

I realise this isn't actually answering your question but may make debugging easier...