I have DB Server with OS win server 2012 R2 with SQL 2012 sp1 DB installed, this DB Server has two instances.
and i have two identical application server with arcmap 10.8 and win server 2019, both application server were connecting normally to DB Server suddenly one of them stopped connecting to one of DB Server instance and still connecting to other instance, an error appears "Failed to connect DB , Failure to access database server"
Knowing that all Server in same network are pinging to each other, no firewall no antivirus. SQL native clients are installed also i installed ODBC, we checked all security policies, nothing worked.
also i checked DB server all services are running, nothing seems unnormal.
All Sql services are running and connecting normally to other clients PCs, except one server.
I did everything, i don't know what's causing this!