The key issue here is the error message "System clock has been set back"
This issue occurs when FlexNet checks file date of some random files on the system and compare with the system clock. If it finds any file that has the date into the future, the license will not work because it would automatically assume that the system clock has been tampered or set back.
Try to locate the files that have the future date and either delete them (if applicable) or change the date. You can look for some free-ware or just try using Windows Explorer > Date Modified > Then select date/month/year into the future. Make sure you can see all hidden/system files.