Back in 2012 I was apart of testing for the rFactor1 exe. The reason for the exe update was the activation used to go through Trymedia. Trymedia was going out of business so ISI now do the activation through their own site.
If you still have and are running a Trymedia version it's possible that this is causing the Win10 issues.
The version I got then and still have is 1255c. As a and b were part of the testing.
If you have this older version it maybe advisable to update it to the latest version exe.
To obtain your rFactor1 Product Key, enter your Purchase Order Number or the email address used when you first activated rFactor.
If your out of activations email to purchase (at) rfactor (dot) net with the subject title "rF1_ISI Activation Renewal" Email address has changed sins rF1 was purchased? Add this to the email with the email address you used.
The new activation page
asks for the email used for first purchase.
It you use the "Already Purchased" to obtain the new "Key". This email with the new Key will go to your old email.
Email rFactor1 support with your old email or original purchase code so they can send you your new key and updated email address.
If your unsure of this, have league race coming up. Install the 1255c to a different location. This will keep your install intact and you can take the time you need to get the new version running.