I bet your here to find out how to fix a ongoing issue since the steam beta was released. So here im going to tell you a simple fix for the error of :
Step 1: Make sure steam is open!
Step 2: Go to settings…
Step 3: Under account you should see “Beta Participation”, Click on Change.
Step 4: Click on the dropdown and check “NONE - Opt out of all beta programs”
Step 5: Restart Steam and let it update and then start FiveReborn and it should now be working! Only for this error!
Thanks hope this helps.