No connection to .NET Application only

I run Software that is divided into 2 separate Apps. One is built on Omnis for Windows, the second is .NET for Windows. Both communicate to a single SQL Database over ODBC.

Frequently I have an issue whereby Hamachi will show me a Direct Tunnel to the SQL Server with a Green Light, I can Ping it with <30ms and I can browse the connected Device but when I run my Software the Omnis App works without issue but the .NET App constantly fails being unable to connect.

I have checked (many, many times) and modified the Firewall at both ends to allow the .NET App to pass traffic to and fro.

The only fix for this seems to be uninstalling Hamachi, including personal settings, and reinstalling which generates a new Hamachi IP Address. Once this is done, and no other changes are made to any devices, the .NET App starts working again.

Any ideas on what could be causing the .NET App to be intermittently declined access over Hamachi?