In general, we recommend using the JFBCContent plugin and configured in the JFBConnect -> Social configuration area. Our buttons should definitely work and will prevent duplicated Javascript libraries from each social network from being loaded, which can cause page loading delays.
Beyond that, in the JFBConnect -> Configuration area, please enable the "Always Parse Tags" setting which may fix your issue. If not, please let me know:
* What version of K2 you're using
* What buttons are configured that aren't working
* A URL where we can see the issue.
I hope that helps, but if you need anything else, just let me know.
Thanks,
Alex