The Error:
Failed to Mount Public Folder database after a lossy failover because the current setting for AutoDataseBaseMountDial. You Must run Restore-StorageGroupCopy before you can mount the Database 
Solution:
Restore-StorageGroupCopy won’t work because it is public folder database.
Setting a Vink by Do not Mount this Database at Startup.
En give the active clustered mailbox server a reboot. Then Cluster service will show that the other node is going online. Then the public folder is back online. After every reboot you must start to check if the public folder online is?