error/mnet/notpermittedtojump

You are not allowed to roam to a remote Moodle or Mahara site. The most likely reasons are...

• The user doesn't have permission to roam (moodle/site:mnetlogintoremote capability)
• The user is a remote user who has already roamed to your Moodle
• The user's username is the literal string 'guest'
• The user's ID is not set (which can't be the case here)

The moodle/site:mnetlogintoremote is not enabled for the Authenticated Users role by default and this, therefore, is the most likely reason.