Thanks GunSquid, I should've mentioned that I had tried that too. Tried again, no change. For the render I did "File > Export > Add to Render Queue", in case there's another way to do it. I rendered as AVI (but I'm guessing that doesn't matter since you said to delete the render anyway).
I'll try posting in the discord!
Update: solved! The issue was that I had the video file selected in the Projects tab (instead of the Composition).
I haven't been able to get this to work yet, I'm using Adobe After Effects CC 2015 on Windows 10.
When I click on "Squirt GIF" I get the "It may appear that After Effects has crashed..." message, but when I press "Yes" the popup closes and nothing happens.
I read the other bug reports, and I found that my c:\ProgramData doesn't have squidyavi.bat, so I figured it was having trouble writing to the file system. I tried reinstalling the script, making sure that "Allow scripts to write files" is checked, and even tried running After Effects as administrator, but nothing's changed. I also tried "Enable JavaScript debugger" but that didn't do anything either.
Anything else I can try to troubleshoot? Where does squidyavi.bat come from, is it downloaded from the Internet at runtime?
Update: solved! The issue was that I had the video file selected in the Projects tab (instead of the Composition).
