[Plugin: Add Link to Facebook] Error trying to authorize

Maybe this is a solution to your problem (from the FAQ):

E01 I get ‘Error validating application’

You have probably entered a wrong App ID or the Facebook application may be deleted. If you didn’t create a Facebook application yet, you should follow the instructions in the yellow box on the plugin page.

If this doesn’t solve your problem, please let me know. If you use the support page, you will probably get faster an answer.