I am not with Laminar Research; just a flight simmer from downunder.
You cannot run more than one version of X-Plane on a PC at any one time. A digital download version requires your PC to be connected to the Internet at all times. X-Plane performs a silent security check to confirm you are not running more than one copy. If detected you will be locked out.
Seems to me the double installation may have contributed to your problem. I would suggest you perform a complete deletion of all versions of X-Plane and start again. If you experience problems in the future run the installer program and it will check for any missing files and or replace corrupted files. The installer program automatically runs when you upgrade to the latest version
Have a look at the log.txt file you supplied using notepad. In particularly look at the last few lines. The message I see is that the flight plan you have created for CANCUN airport is most likely contributing to your problem as well. When you perform a complete new installation this flight plan problem will disappear.
Test the system works before trying the Cancun flight.