On all systems, FMP URL links can be opened by only one program. If you've installed multiple instances of FileMaker, URL links will open, by default, in the last version of FileMaker installed. If you'd like to change the default FileMaker version that is used for FMP URL links in Windows, you can modify a registry key, rather than uninstall/re-install that version of FileMaker.
First, while this change should not affect your system in a devastating way, if you don't implement it correctly or modify/delete the wrong keys, you make render your system unusable. Therefore, a warning from Microsoft: "Using Registry Editor incorrectly can cause serious, system-wide problems that may require you to re-install Windows to correct them. Microsoft cannot guarantee that any problems resulting from the use of Registry Editor can be solved. Use this tool at your own risk."
There is only one registry key value that must be modified for this solution. If you can't find this key in your registry, it would probably be best to just uninstall/re-install the version of FileMaker you'd like to open FMP URL links by default.
1. Open Regedit and Backup your registry. (Instructions Here)
2. Find the following key:
3. Modify the "(Default)" value with the path to the version of FileMaker you'd like to use by default with the following added at the end: %1. for example:
C:\Program Files\FileMaker\FileMaker Pro 15 Advanced\FileMaker Pro Advanced.exe %1
You may need to restart FileMaker to see the changes take effect. This change should update your system to open FMP URL links with the version of FileMaker you specified in the registry.
I'd like to extend a thank you to Rick Lindberg of InterLink Network Services, Inc. for helping with this solution!