Invalid Scopes: manage_pages. This message is only shown to developers. code example

Example 1: facebook invalid scopes manage_pages. this message is only shown to developers

This error is because of facebook has updated permissions that you are looking for to new ones refer latest permissions this documentation shows latest permissions and update yours https://developers.facebook.com/docs/facebook-login/permissions

Example 2: facebook invalid scopes manage_pages. this message is only shown to developers

just remove manage_page from scope attribute

<fb:login-button size="large" 
 scope="public_profile,email,pages_show_list,read_insights,manage_pages" 
 onlogin="checkLoginState();">
 Click here to sync
</fb:login-button>

to 

<fb:login-button size="large" 
 scope="public_profile,email,pages_show_list,read_insights" 
 onlogin="checkLoginState();">
 Click here to sync
</fb:login-button>