I have installed Mashshare plugin on my WordPress blog and all was well for first day. On the second day, my dashboard started to show an error message:
Error: Unknown Error
Your Facebook Access Token has been expired or is invalid. Remove the invalid access token from MashShare->Settings->Networks or generate a new one. Your MashShare Facebook Shares will not be refreshed any longer. Read here how to renew the Facebook access token. Fix it and press the button: [CHECK AGAIN]
I am not able to "Verify Access Token" from the button in the Settings > Networks page. I have created an upgraded Facebook Access Token by going to "Debug" in developers.facebook.com as said by Mashshare. Entered the new access token in the WordPress dashboard, still receiving the error. Not able to Verify Access Token. It seems a validation error. Or I have to wait for some time to update on FB server. I will keep you updated about this problem and it's solution.