The maker isn't that great, if it doesn't upload, you just have to try again. :/

i've done it quite a lot

It failed i tried to make one called: Eseepea sux ate 2 but it wouldnt upload to the workshop or get in my game. it worked the first time but it never appeared on the nextbot npc menu =(

Im having the same issue, i managed to catch the error message during the uploading at the correct time. During the command window for the uploading it gives me a error saying "Error opening addon (Does the file exist?)"