You could try deleting all of the saved settings and files used by the software by following the instructions here:
https://www.simplify3d.com/resources/faq/#quest-6350
Feel free to copy/backup those files first if there are important profiles you need to save.
If it doesn't open even after making that change, you could check to see if there is an anti-virus software that might be preventing the software from opening. Another idea could be trying it with any extra peripherals unplugged (extra monitors, 3D printers, etc).