I have a mod (1773746472, friends-only right now). It was quite difficult to upload, but I eventually found a trick to make it work: start TTS, start the mod from the local save file, then immediately upload it.

However, I want to update it (via the Update Workshop tab), and that trick isn't working. Each time I try I get:

Error Steam share mod: k_EResultFail

(which is also what was happening with the initial upload)

If I put the cover URL in the Thumbnail box rather than leaving it blank, I get instead

Error Steam share thumbnail: k_EResultFileNotFound

If I put in a new thumbnail URL, I get:

Error Steam share thumbnail: k_EResultFail

Is there an alternative upload mechanism so that I can get the thing where my testers can see it?

(Linux, current version.)