-1 / empty / <null> means no response received.
This is either your network was down, the proxy wasn't working, something on your machine blocked the request / the site server timed out and didn't respond in time (unlikely but does happen)
If using a proxy, test it:
Please confirm your proxy is working, more info on how to do that here:
viewtopic.php?f=15&t=3453
If the proxy appears to be working fine, please run the action again as it could have been a network "blip".
If the issue appears to be persistent, please check your anti virus / security software as they *may* block the app from the accessing the network: the two most common are:
* Windows Defender
* Smart screen
Make sure the applications program files folder:
c:\program files (x86)\twitterdub
is whitelisted and / or all the .exe and .dlls in that folder.
Please let me know what operating system you are using and how you run the program: At home / on VPS / In VM?
Regards,
Martin