It's mandatory with "MetroPCS/T-MOBILE Device Unlock App" Service to check BEFORE place your order that your phone show "Not Eligible for Unlock" error.
If instead you have the error "Server not responding" this mean your phone is not even able to communicate with MetroPCS Server (Communication Error)
You need to fix this problem before order since we do not accept complaint / refund request about this specific error.
However we do have some tips to get rid of this error:
1 - Make sure you use the original Stock ROM from MetroPCS since it will not work if you flash your phone with any custom Firmware from T-Mobile, CyanogenMod, or even an Unbranded ROM.
2 - However make sure you're using the last version of MetroPCS Firmware for your Cell Phone.
3 - Finally (after upgrade) perform a Hard Reset on your Cell Phone (you'll find Hard Reset method on: http://www.hardreset.info or check on YouTube).
4 - Turn off 3G/LTE and force the use of a local WiFi Hotspot.
5 - Make sure you use home Wifi (and not a public/company WiFi since they might use firewall, vpn, etc... that will trouble communication)
If none of these recommendations work for you, then we don't have solution.
If you find a way to fix this problem with another method, please let us now so we can help better our community.