App suddenly won't open after latest Mojave security update

So I updated to the latest security update in Mojave, and had an application, DocFetcher, suddenly stop working.

Double-clicking on it simply makes the Dock shake for a second. Reinstalling did nothing.

According to [this thread on the DocFetcher forums](https://sourceforge.net/p/docfetcher/discussion/702424/thread/ee550dd7e4/?page=0), this issue -- which affects only some people -- might have something to do with it being from unidentified developers and the Internet. I know Catalina has new restrictions on that, but perhaps this security update also affects them? I'm not sure.

In Security & Privacy preferences, it says "Allow apps downloaded from app store and identified developers"... I've tried control-clicking on the app and opening, etc. -- no dice.

It all seemed to work fine before this update.

Any advice? Thanks.