In case dimension "Link to post" not returning any data for your queries, or it is working only with certain accounts, it is likely caused by insufficient permissions. You need to grant “manage_pages” permissions to relevant Facebook pages for Supermetrics connector when authenticating to be able to retrieve this data.
To fix the problem, you will have to follow these directions for resetting the app permissions:
And during the re-authentication process you will have to select the relevant pages:
And make sure that the "Manage your Pages" is enabled: