What OS? On Windows the argument limit be quite low. What does the console output say?
Hi, sorry:
IOException: Failed to exec fpcalc: Cannot run program "C:\Program Files\FileBot\fpcalc.exe": CreateProcess error=206, Filename or extension too long (manual translated by me)
java.util.concurrent ...

Hello.
I'm facing the same problem here using the latest beta available as of today, because I've found this problem fixed here (https://www.filebot.net/forums/viewtopic.php?f=6&t=3818) and had to donwload it at first place.
The strange thing is that I've renamed some files an hour ago.
If I try ...