Impossible to mention a Facebook page
Incident Report for AgoraPulse
We’re currently impacted by a Facebook bug, preventing some users to mention a Facebook page for the last 4 days:

That's why you might receive the error message “Internal server error" trying to mention a page within our publishing tool.
We're very sorry for the inconvenience: we will update this incident as soon as we have more information from Facebook.
Posted 12 days ago. Oct 08, 2018 - 11:04 CEST
This incident affects: Facebook Publishing & Data Processing.