Unable to sign into Plex Account with Media Server

Plex finally made Xbox 360 Plex app availabe to everybody but I am not able to get it in working condition.
Xbox Plex app does not find the server. In order to get it find the server, the server needs to be signed into Plex account
from dashboard > Server > General page. But it tries to connect and gives a message that the problem occured. No other specific info.
Heres what I know
I am able to login to plex.tv with my account. So the username and password are ok. I tried both e-mail and username version.
Xbox shows up in my devices lists so this device is able to connect.
Media server works all fine within local network
The Plex dachboard is accessible through WAN port, so no issue there.
The Plex media server has software manually updated - version 0.9.12.11.1406.
Any clues what else can I try of check to make it work?

The problem must be with Synology. I have installed Media server on my laptop and everything works.
Heres whats in Synology log file:
Sep 13, 2015 09:41:01 [0x4b05f470] DEBUG - Request: [192.168.1.230:64557] PUT /myplex/account?username=myusername&password= (3 live) GZIP
Sep 13, 2015 09:41:01 [0x4b05f470] DEBUG - Auth: We found auth token (xxxxxxxxxxxxxxxxxxxx), enabling token-based authentication.
Sep 13, 2015 09:41:01 [0x4831c470] DEBUG - Auth: Refreshing tokens inside the token-based authentication filter.
Sep 13, 2015 09:41:01 [0x4b05f470] DEBUG - Auth: Refreshing tokens inside the token-based authentication filter.
Sep 13, 2015 09:41:01 [0x4b05f470] DEBUG - HTTP requesting POST https://plex.tv/users/sign_in.xml
Sep 13, 2015 09:41:31 [0x48612470] DEBUG - WebSocket: processed 0 frame(s)
Sep 13, 2015 09:41:41 [0x4b05f470] ERROR - Error issuing curl_easy_perform(handle): 6
Sep 13, 2015 09:41:41 [0x4b05f470] WARN - HTTP error requesting POST https://plex.tv/users/sign_in.xml (6, Couldn’t resolve host name) (Couldn’t resolve host ‘plex.tv’)
Sep 13, 2015 09:41:41 [0x4b05f470] DEBUG - MyPlex: Did update authToken for myusername (returnCode: -6)
Sep 13, 2015 09:41:41 [0x4b05f470] DEBUG - MyPlex: Got a token poked, let’s act on it.
Sep 13, 2015 09:41:41 [0x4ad71470] DEBUG - Sync**: myPlexSignOut**
Sep 13, 2015 09:41:41 [0x48900470] DEBUG - Completed:

Yep, thanks. I did figure it out finally Found the puzzle piece from other thread also, that is Network issue. Didn’t even occur to me. I had to change my router a while ago and in Synology I had wrong gateway and DNS server settings that pointed to wrong address 192.168.1.254 (old router). It is now 192.168.1.1. Sometimes the solution is as simple as that. Everything works now. Hope it helps someone in the way. Thanks!