This is usually an issue with special characters in the project path. Can you go to c:\programdata (it may be hidden) and find the "squidyavi.bat" file and paste the contents of it here (edit it in notepad, then copy and paste)
Thanks for your reply. Here are the contents of the .bat file you requested. I'm assuming it is the "_" in the name that messed it up, as the original file was named "Comp 1", but the renaming algorithm added the "_4" (this was my fourth attempt, versions _2 and _3 also were previously generated by AfterEffects...)
cd\ cd "C:\Program Files\Adobe\Adobe After Effects CC 2018\Support Files\Scripts\ScriptUI Panels\GIFsquid\"
GIFsquidavi.bat 24 1500 "D:\Windows\Documents\WebWorks\Brittleknee\Gif Creation\1\Comp 1_4.avi" "D:\Windows\Documents\WebWorks\Brittleknee\Gif Creation\1\GIFsquid_Output" 0.5 480x "" "Comp 1_4.avi" false
exit
Actually, underscores are allowed characters, so it shouldn't be that. Does the issue persist after restarting after effects? Another thing to try is clearing the render queue and deleting any leftover AVI files from failed GIF creation and then trying again. I've sometimes seen AE fail to render anything after pressing g Squirt. Usually manually rendering and then trying again fixes this.