Are you logged into Steam and Launching the Mod Tool from Steam?

Also if you an get a screenshot of the error message or make a video of it, that would help. The text doesn't appear in my code. The closest to that is: "Something Broke" and "Something Probably Broke..." The latter of which is k_EItemUpdateStatusInvalid which is from Steam saying the mod is corrupted or network issue or a connection issue to Steam.

https://github.com/gearcity/GearCity_ModTools/blob/master/SteamWorksUploader.cpp

Something probably broke sounds right!
I am logged in, will try to snap a screesnhot.

If that is the case, it narrows it down to k_EItemUpdateStatusInvalid, which like I said can be many different things Steam is reporting back. Not very helpful (which is why the error message isn't helpful.)

When I get in the office this evening, I'll try to update my little demo logo mod and see if it works. That will at least narrow it down if it's Steam's fault, my fault, or your fault. :)

I just gave it a run on my Windows 10 install and it works fine for me.

A few things to check:
- Do you have the original manifest file? Steam might be blocking you from updating without that file.

-Any changes you make to the mod name, it needs to be changed in the ModFile.xml and all the files that has the old names. For example, if I was renaming 'VENT LOGOS' to 'BetterLogos' then mod_VENT LOGOs_MiscArtwork.zip and mod_VENT LOGOs_PlayerLogos.xml would need to be changed to mod_BetterLogos_MiscArtwork.zip and mod_BetterLogos_PlayerLogos.xml respectively. Then in ModFile.xml, I'd need to go over every text with 'VENT LOGOS' and change it to 'BetterLogos'.

-If you change the logo, be sure it's in the same folder as the rest of the mod files.

Hey, I did not get back to updating the mod yet, as I am not near this computer atm. I can however confirm I did not change the name or logo and used the original manifest.