I've painted a texture for that model but Sketchfab can't accept 2.8 Blender files.
Such a bummer.
Do you get any specific error message with sketchfab? Because I've been sending files done with 2.80 and even newer development builds (2.81 alpha). However, if I remember correctly, you need to apply most modifiers - think it had issues with mirror modifier I think - might be worth checking.
>>Do you get any specific error message with sketchfab?
No, its regular "Error 20" message. The platform doesn't accept Blender 2.8x files yet (same goes for Sketchfab Import/Export add-on).
I've tried some ways with exporting different formats (didn't help) and finally came up with the only solution that worked:
Delete 2.80 / Install 2.79 / Do that lesson again / Upload the result to the Sketchfab.
Error 20 message, for now just means that they were unable to convert your file properly to work on their website. It will usually happen if you have any object that's hidden from view or hidden from render in your .blend file. Remove those, and it will most likely work. (I just did a test a few minutes ago)
Why delete 2.80?
You can have both installed (unless you have very little space, which seems unlikely in these days).
I have five different Blender versions installed.
Also, can't you just Append it in 2.79?
There is certainly no harm in re-doing an exercise, but there are many cases where you do not want to re-do all the work...
Totally agree with "no harm in redoing". I'm enjoying these lessons very much and personally I'd like to see more of them. Too bad I've missed that august course with texturing/baking practical routine. Hope CG will implement it as a part of 2.8 flow later on.
As for various versions, yes, I had 2.79 and 2.80, but pretty soon there was only 2.80 left. And when I tried to install 2.79 again (yesterday, to complete that lesson) I had some "there is a higher version of that program" pop-up.
Anyway, it's all good now, thanks!