Hi there, hokahey,
I want to make sure you're able to update your Quickbooks company file to the latest version.
You're able to update your company automatically to 2019 provided you have a QuickBooks for Mac 2015 file on the same computer. You just need to make sure the old file (2015) is saved in your Documents folder. Also, when updating the file, only the 2019 version should be open and running. Close any other programs that may intervene the conversion process.
To open the file, go to the File menu and select Open Company.
Another option is to back up the 2015 file and restore it to QB Mac 2019. Let me guide you through the steps:
Step 1: Create a back up copy.
Step 2: Restore the file.
However, if you're converting a QuickBooks for Windows 2015 file to Mac, you have the option to export the file. To convert, go to File menu, then select Utilities > Copy Company File for QuickBooks Desktop for Mac. You might find this article helpful: Convert a QuickBooks Mac file to QuickBooks Windows and back again
That should do the trick, hokahey. Please let me know if you have any questions about the process. I'm here to help you get back on track. Have a good one!