I purchased FMP 17 yesterday [11/16] and installed it on my MacBook Pro running Mojave [10.14.1]. It installed OK. The first thing I did was to open an existing solution created in FMP 14 and it worked just fine. I saved a copy as a new FMP 17 solution. When I tried to open either the new FMP 17 version OR the original FMP 14 version, I get an 'unexpectedly quit' error. No matter what I do, I can't seem to re-open any of my solutions.

I've deleted and reinstalled the new FMP 17 app and continue to get the same results.

Any suggestions would be welcome.

After some more testing, I found that if I select 'OPEN', it uses my FMP 14 as the default application. However, even though FMP 14 is still installed on my computer, it still presents the 'unexpected error' message.

If I select FMP 17 to open the solution, everything works fine.

Only versions 16 and 17 will be supported on Mojave. I say "will", because there are currently some issues which are expected to be fixed by the end of this year:
https://support.filemaker.com/s/article/FileMaker-and-macOS-10-14-Mojave-compatibility?language=en_US

The last Mac OS to support version 14 was El Capitan - that's 3 major versions back:
https://support.filemaker.com/s/article/FileMaker-Pro-operating-system-requirements-all-versions-1503692917754?language=en_US

Unfortunately, FMP has a very poor record of surviving Apple's OS upgrades (I believe things are better for Windows users).

 

1 hour ago, Arnold Hooton said:

I found that if I select 'OPEN', it uses my FMP 14 as the default application.

You can change that by doing Get Info on one of your files and selecting Open with: + Change All.