Unable to Connect the Database shows error SQLNCLI error

I think something might be wrong or missing with your SQL Server client on the monarch server. 

I did read something in some of the recent Monarch Server release notes that there was an issue with SQL installation scripts, it could be related.

I would contact Monarch support for assistance to ensure you have a good build of the installer and get help with your installation or upgrade.

These links might help also-

documentation on installing sql server native client

https://docs.microsoft.com/en-us/sql/relational-databases/native-client/applications/installing-sql-server-native-client

installer download link for sql server native client

https://www.microsoft.com/en-us/download/details.aspx?id=50402

Also, If Sql Server Native Client was already installed, you might want to try doing a "repair" in add / remove programs - that should fix most problems

Thanks  Thomas