Again, please write on the mailing list. Many people besides me will be happy to help.
Are you seeing those errors from UI? If so, my guess is
1) you didn't specify the remote address (hostname or ip)
2) you checked "remote capture command" flag, but you didn't specify the actual remote capture command
For a better sshdump debug, please provide the full options you set in the options dialog. If your version is recent enough, you can find a debug flag (and a debug file path) in the options dialog. They've been added to trace the actual cmdline call that wireshark runs against the extcap.
If the provided infos don't help you, I suggest you to install a development version (that should has the debug options) and start from there.
Hope it helps.
Dario.