Cars are not selling due to universal fittings not being fitted to the vehicle however, they are - Photos attached
debug.txt (28.7 KB)
autosave.zip (115 KB)
Have you got the relevant slot placed and with the correct upgrade for it to fit those parts?
So just downloaded your save and checked and you don’t have the correct slots on your map to be able to fit those upgrades which is why the car doesn’t have them.
If you look on the item in technologies in research it tells you which slot can be upgraded to fit it. I’ve included two exampled below of the slot and where you need to enable the upgrade.
This one shows the power steering upgrade that needs to be bought at the fit steering wheel slot.
This one shows the heater slot that needs to be bought at the fit dashboard (or i think fit controls slot if you break it down another tier).
At the minute you’ve only got the basic slots for each area placed. You’re going to need to start breaking your production line down into sections more to get the upgraded to work.
Ahh okay thank you very much! I tried to research for the issue but had no luck 
It’s not an issues I suppose, more just a feature of the game. Probably why you couldn’t find anything.