In case the forgotten password doesn't have to do with your company file not opening, try logging into a different computer and see if you encounter the same thing. If you're able to open the company file, look into this article for some troubleshooting steps to fix the issue: Resolve Problems Opening QuickBooks Desktop or your Company File.
You should be able to access your files after upgrading QuickBooks with the above information. Let me know how things go once you've tried the steps by leaving a reply on this thread. I'm always here to help. Have a great rest of the week.