When you click on the callback URL in the Google popup dialog, the copy of FileMaker Pro on your computer will be opened with that URL. If you have multiple copies and versions of FileMaker Pro installed, the version you expect may not launch. Generally, the copy of FileMaker Pro defined as the 'default' for the .fmp12 file suffix will launch. For this reason, behavior can seem incorrect or unpredictable when multiple different copies of FileMaker are installed.
If you have a desire to run the PBS Widget file on a different server than the one your solution is hosted on, you will need to edit line 37 of the Map_Widget script as shown below to point the script at the correct server.