Can't update workshop submission's thumbnail

[KleinerHl]

Hello,

I've been trying to update the thumbnail of my workshop submission after I noticed that there's something wrong with it.

I tried the [URL="http://wiki.garrysmod.com/page/Workshop_Addon_Updating"]wiki's[/URL] way but it didn't work, here's what I got:

[quote] [I]Garry's Workshop Publisher 1.0
Setting breakpad minidump AppID = 4000
Steam_SetMinidumpSteamID: Caching Steam ID: 76561198118067442 [API loaded no]
Error opening addon <does the file exist?>[/I] [/quote]

I tried the normal update way but all what happened was the .gma updating and the thumbnail not.

Is there a way to update it? Thanks.