This error is typically related to the Easy Anti Cheat software. Please try and install or repair the EasyAntiCheat software. 

You can do this by going to C:\Program Files (x86)\iRacing\EasyAntiCheat (or C:\Program Files (x86)\Steam\steamapps\common\iracing if you purchased and installed through Steam) and run the set up file from there by right-clicking and selecting Run As Administrator. 

If after that you are still having this issue, please look in your Documents/iRacing folder and see if you have a file in there called sim_launch.txt. If you do, please email this to 
Also, look in your Documents/iRacing/logs folder and send us any log files that are in there. 

Also, can you provide the loader.log from the following location after one of the failures? 
If you cannot see that folder, you can paste the following text into the explorer bar and it will navigate you there.