Fixing Facebook posting error: "The user must be an administrator of the page in order to impersonate it."
This error message may be popping up because the account who originally added the Facebook Page to MyLocal is no longer an administrator, and MyLocal is still trying to use their credentials.
To resolve this issue, go to https://www.facebook.com/settings?tab=applications and revoke MyLocal from Facebook by clicking the x next to the app. Then, remove the page from MyLocal by going to your user profile (top right button), click the cog icon for settings and then choose Social Network Settings and then Remove/Reconnect Facebook from MyLocal.
Now, re-add the Facebook page using your own credentials to be able to post again.