Q: Nothing worked!
A: Make sure you are using latest Spectrum and latest plugins, most likely the issue was already fixed but your version is 1-2 years behind.
Q: Still nothing worked!
A: Check Spectrum logs for error messages.
By default it is
/var/log/spectrum2/<transport jid>/spectrum2.log for the transport itself
/var/log/spectrum2/<transport jid>/backends/backend-N.log for protocol plugin.
Q: Some protocol plugin not worked!
A: If it is a libpurple protocol plugin - try it with Pidgin or Finch first directly without Spectrum.
pidgin -d and
/var/log/spectrum2/<transport jid>/backends/backend-N.log - they should be identical.
If you get some info - check known issues and file new issue if needed.
Q: It works with Pidgin (directly) but not working with Spectrum!
A: In this case it would be good to study your client XMPP logs for some unusual cases. Be prepare to show it when submitting an issue!