Look at the sylink log it will give you the information if the gup is working or not.
Requesting the GUP for the update
05/22 00:06:28 [3504] <mfn_MakeGetLUFileIISUrl:>Requested Content Path is: /content/{812CD25E-1049-4086-9DDD-A4FAE649FBDF}/80521036/delta80520034.dax
05/22 00:06:28 [3504] <GetLUFileRequest:>IIS URL: /content/{812CD25E-1049-4086-9DDD-A4FAE649FBDF}/80521036/delta80520034.dax
05/22 00:06:28 [3504] <GetLUFileRequest:>http://<GUPNAME>:2967/content/{812CD25E-1049-4086-9DDD-A4FAE649FBDF}/80521036/delta80520034.dax
Example of a Sylink log from a client to a GUP requesting an update:
<LUThreadProc>Starting LU download.
03/24 14:29:04 [2232] <LUThreadProc>Got a valid context from GetCurrentServerEx
03/24 14:29:04 [2232] <LUThreadProc>Setting the session timeout on LUSession to 2 min.
03/24 14:29:04 [2232] <mfn_MakeGetLUFileIISUrl:>Requested Content Path is:
/content/{C60DC234-65F9-4674-94AE-62158EFCA433}/80324005/delta80323019.dax
03/24 14:29:04 [2232] <GetLUFileRequest:>IIS URL: /content/{C60DC234-65F9-4674-94AE-62158EFCA433}/80324005/delta80323019.dax
03/24 14:29:04 [2232]
<GetLUFileRequest:>http://192.168.2.5:2967/content/{C60DC234-65F9-4674-94AE-62158EFCA433}/80324005/delta80323019.dax
03/24 14:29:04 [2232] <GetLUFileRequest:>NEW download: C:\Program Files\Symantec\Symantec Endpoint Protection\LiveUpdate\LUF5.tmp
03/24 14:29:04 [2232] <UpdateLUFileList:>Updating existing Download File List with : {C60DC234-65F9-4674-94AE-62158EFCA433}80324005
03/24 14:29:04 [2232] <UpdateLUFileList:>Updating existing Download File List Temp file name from: to C:\Program Files\Symantec\Symantec Endpoint Protection\LiveUpdate\LUF5.tmp
03/24 14:29:04 [2232] 14:29:4=>Sending HTTP REQUEST to download LU file
03/24 14:29:05 [2232] 14:29:5=>HTTP REQUEST sent
03/24 14:29:05 [2232] <GetLUFileRequest:>IIS return=200
03/24 14:29:05 [2232] <mfn_DoGetLUFile200>Downloading LU file from server. Moniker: {C60DC234-65F9-4674-94AE-62158EFCA433}Server File Path:/content/{C60DC234-65F9-4674-94AE-62158EFCA433}/80324005/delta80323019.daxLocal Path:C:\Program
Files\Symantec\Symantec Endpoint Protection\LiveUpdate\LUF5.tmp
03/24 14:29:05 [2232] <mfn_DoGetLUFile200>Content Length => 35403
03/24 14:29:05 [2232] <UpdateLUFileList:>Updating existing Download File List with : {C60DC234-65F9-4674-94AE-62158EFCA433}80324005
03/24 14:29:05 [2232] <UpdateLUFileList:>Updating existing Download File List Temp file name from: C:\Program Files\Symantec\Symantec Endpoint Protection\LiveUpdate\LUF5.tmp to C:\Program Files\Symantec\Symantec Endpoint Protection\LiveUpdate\LUF5.tmp
03/24 14:29:05 [2232] <mfn_DoGetLUFile200>LU Content Downloaded. Moniker: {C60DC234-65F9-4674-94AE-62158EFCA433} Target Seq:80324005 Full version:0 Delta Base Seq:80323019
03/24 14:29:05 [2232] <PostEvent>going to post event=EVENT_LU_DOWNLOAD_COMPLETED
03/24 14:29:25 [2224] <CSyLink::mfn_DownloadNow()>
03/24 14:29:25 [2224] </CSyLink::mfn_DownloadNow()>
03/24 14:29:30 [2232] <PostEvent>done post event=EVENT_LU_DOWNLOAD_COMPLETED, return=0