Hello my questioning friend.
How did you install everything?
Was AC previously virgin so vanilla?
Did you have any apps installed?
You don't give any information. Only it crashes.
Does your CSP version support your SOL version?
It's like when you call a garage and say your car is making a noise and you want to know what that is. Even the best car mechanic cannot do anything without more precise information.
This error message can mean anything or nothing.
I can only tell you from my experience that if you follow the installation instructions from CSP and Sol exactly, it works. You should always make a backup copy.
My plan would be as follows:
First uninstall Assetto Corsa completely via Steam. Various data remain.
The folder must also be deleted. You have to uninstall this manually. No residual data may remain. Now delete the folder in the documents folder. Those are just your stats, but that's better.
You never know. Now delete the csp folder.
For me it is in user/user/appdata/local. It's called AcTools Content Manager. At least for me.
Done. Now the last byte should also have been removed.
Install Assetto. Create backup copy.
When it works Download the latest CM and follow the installation instructions 100 percent.
If AC starts and runs via the Content Manager, delete old Backup and create a new backup copy.
Download SOL and follow the installation instructions 100% again.
Now set exactly as it says in the SOL documentation. Then it should work.
I know that takes time. There is no quick fix. Fast always means doing it twice.
Another tip.
If it works and you want to install mods. Always and I repeat always install by hand.
The same applies here. Install a mod. Testing. No Backup needed.
Only then install the next mod etc.
It takes time, but you know immediately which mod is causing problems and you can delete it.
Don't rely on drag and drop. Not every modder sticks to the folder structure. Unfortunately.
There are enough topics that confirm this.
It all sounds cumbersome, old-fashioned or overcautious, but that's how I've been doing it since MS-DOS 6.22 and I'm fine with it.
If, despite my own caution, problems should arise, it is usually only a matter of settings and these are quickly resolved.