Bit more info relating to the issue I had, in case it helps. Windows 10 64-Bit. I purchased Gladius from Matrix Games as a physical shipment, on DVD.
From the disc for the main game I installed Gladius-RelicsOfWar-MultiSetupRelease-V1.10.01.00.exe
This was followed by Gladius-RelicsOfWar-MultiPatch-v1.12.00.00.exe which was also on the disc.
I had also purchased the DLC packs for the Adeptus Mechanicus and T'au as physical copies on DVD. The disc contents for each of these turned out to be identical to the main disc for Gladius so I just ran the v1.12.00.00 patch file from the disc, selected Activate DLC and inputted the key. I did this with both discs.
Once that was done I loaded up the Game Menu from Windows' Start Menu, clicked the Check For Updates option and TrueUpdate successfully upgraded my Gladius install to v1.13.01.
Now when I check for updates TrueUpdate tells me that "There is a newer version of Warhammer 40,000: Gladius - Relics of War available." so I clicked Next.
The Downloading File window pops up but the file it's downloading is always Gladius-RelicsOfWar-MultiPatch-v1.13.01.exe which is the version that's already installed.

- Gladius_Wrong_Update_1.png (17.56 KiB) Viewed 5326 times
Once it's downloaded the installer runs and the welcome screen for that tells me it is for v1.13.01 and if I click Next anyway I then get a screen telling me that I'm alredy up to date and giving me the options to Activate DLC, proceed with the reinstall anyway or cancel.

- Gladius_Wrong_Update_2.png (116.14 KiB) Viewed 5326 times
I've tried using the reinstall option from that window but it's still doing the same thing as before once the installation was completed and I reloaded the Game Menu.
I hope this helps! I am really enjoying the game and have just bought some more DLC.