Thank you for the post.
I previously responded to your identical post here:
This error will be thrown if the FileMaker Pro trial is not first opened and the Contacts.fmp12 is instead double-clicked.
This is a limitation of the trial, as you must first open the program and click "Try it" before a file will be able to be opened via a double-click.
Open the FileMaker Pro trial and then click File > Open… and choose the file to be opened.
If recent changes to the file are not reflected, I suggest searching the computer for all files with ".fmp12" extension to see if perhaps more than one copy of the file was saved to multiple places.
What exact steps were taken to open the file?
With the file opened, make changes to the layout, then quit and reopen the program. Did the new changes save?