problem started when sysadmin received error that model is recovering.
Sometime later vendor tried to do some upgrades to the database. When they restarted SQL Server it failed to start.
Looking at error log. I found the following error
Error The database 'model' is marked RESTORING and is in a state that does not allow recovery to be run. Error: 927, Severity: 14, State: 2. Database 'model' cannot be opened. It is in the middle of a restore. Could not create tempdb. You may not have enough disk space available. Free additional disk space by deleting other files on the tempdb drive and then restart SQL Server. Check for additional errors in the event log that may indicate why the tempdb files could not be initialized.