there are quite a few different factors that can cause this, make sure you are definitely logged in and in online mode on steam, and that you have agreed to the steam workshop T&C (this should pop up automatically if this is the case).

what message is shown after the failed upload?

I've just checked an your workshop items are hidden since you need to sign the workshop agreement. please check this: https://psteamcommunity.yuanyoumao.com/workshop/workshoplegalagreement/

Fixed. Marklin route is up, it's pretty much finished, though needs a few minor details. working on my second one now.