Facebook App - Cannot Disconnect FB Account

[JOIUSS]

I tested my FB account in a client account I'm collaborating on by using my FB account login details.

The disconnect button doesn't work.  So I'm unable to login into their actual FB account.

I have tried deleting the app to start again, but, my personal details are still there and unable to disconnect.

I'm going around and around in curcles, please help!

[colinw]

Same question but obviously can't get an answer here.