Recently in Dynamics 365 Finance and Operation I have got an error in which it says "Unable to recycle AppPool 'AOSService' running Site 'AOSService'. Check your IIS/Azure Environment for correct deployment". This error occurred while synchronizing the database.
Reason of this error is because AOSService in Application Pool got stopped.
Note: Open IIS Manager and Run as Administrator.
For resolving the issue, all you need to do is to run the AOSService in Application Pool.