Darth Wazawai

Did you have a custom profile path? As in did you move the game folder from where single player mode made it. If not try sp and see if your profile is still there as well.
 
If you did you'll have to set the path to your profile before you can load the game. I'm on my phone but setting your is no different than doing it in steam (I'll find it and edit this post)
 
Here we go:
https://steamcommunity.com/app/227300/discussions/0/648817378385203368/
 
If this is the case, you should create a shortcut for said options as the shortcut won't lose them and becomes as easy as install and running the new game version this is what I do.

It's in the rules, police cars and their accessories are for admins only in mp if you want to drive the police car version you'll have to copy the mod into the sp game mod folder
 
Edit: mis read... Try buying a new car or do a new paint job and avoid the last 2 paint jobs on the list

You need to do a few extra steps.
http://forum.scssoft.com/viewtopic.php?f=34&t=164103&start=70#p334568
Select 3 reload into the game quite (auto save). Now you have 2 files.
Decrypt the .0 version
Proceed as intended.
Reason for 3 and not 2 you get a second save file saving you the hassle of coping it yourself.