If you patch 8.1 to 8.1.1 and your Mobile and Remote Access stops working you need to regenerate your certificates.
During the patch from 8.1 to 8.1.1 the XCP/XMPP router service is being introduced. When modifying anything related to XCP/XMPP on VCS or Expressway you need to regenerate the certificates. The same applies when you modify or add XMPP chat node alias.
The certificates need to be regenerated on Core and Edge. Once applied a restart will have it take effect.
The documentation does not currently reflect that this is a required step and should be updated soon.