Registration form just dissapeared after upgrading from 3.6.4 to 3.6.5.
/component/users/?view=registration
There was only blank page, no errors (error_reporting set to maximum in the backend and turned on in php.ini). I solved this issue by replacing:
components/com_users/models/registration.php
from 3.6.4 release.
| Labels | Added: 
? | ||
 
                | Status | New | ⇒ | Closed | 
| Closed_Date | 0000-00-00 00:00:00 | ⇒ | 2016-12-31 09:09:14 | 
| Closed_By | ⇒ | Frostbourn | 
 
                +1, thank you bertmert.
| Status | Closed | ⇒ | New | 
| Closed_Date | 2016-12-31 09:09:14 | ⇒ | |
| Closed_By | Frostbourn | ⇒ | 
 
                Did the fix by mbabker solve your issue?
Do you have a template override in place?
 
                @Frostbourn is this still an Issue?
| Category | ⇒ | com_users | 
| Status | New | ⇒ | Information Required | 
 
                Unable to reproduce.
Installed Joomla 3.6.4.
Upgraded to Joomla 3.6.5.
Registration form appears and works as expected.
| Status | Information Required | ⇒ | Closed | 
| Closed_Date | 0000-00-00 00:00:00 | ⇒ | 2017-04-17 22:41:49 | 
| Closed_By | ⇒ | zero-24 | 
 
                Closing again. As this is fixed by the change posted above.
I don't know if it's really related but did you test this change already:
3722260