Vivek,
What devices / OS version / Agentry client version are you deploying?
Another one that I have seen recently being a culprits
- VPN Connection Stability
The quickest way to check connectivity is to use the server URL in your browser. If you get the I am here! message without any certificate errors that your networking connection is in place. This will usually rule numbers 2 & 3. Number 4 is typically only an issue with Win CE devices if you are current with your SMP server/client versions so just something to be aware of for your initial connection testing.
The challenging ones are really #1 and mine above if using a VPN depending on your device. These are a challenge because they are transient. Meaning it will work fine one day but the next you will suddenly get the Error 14 errors using the same device on the same network to the same server. In these cases I don't see a test app providing much help and unfortunately it is very difficult to diagnose and fix in many cases as it is beyond your control.
There just isn't enough capability to determine why the Error 14 is suddenly occurring in most cases.
--Bill