From time to time a pop-up window appears asking you to update access token because the access was expired. You can find details about this expiration here.
How can you refresh your tokens?
Go to your profile and find “Social Profiles" section.
Click on “Edit” icon.
Click on "Update Access Token". Do not forget that you have to be logged in to your page's social platform and you must have admin/editor roles on these pages.
Wait until you see "token updated" notication and save!