HafeezAtobajaye You need to disabled development mode within your Facebook application.
STEP 1:
First, log into Facebook Developer -> Your App
In Settings -> Basic -> Contact Email. (Give any email)
STEP 2:
Lastly, in the 'App Review' Tab : change
Do you want to make this app and all its live features available to the general public? Yes
And you should be rid of this issue.