"There was an error processing this request. Please refresh this page."

ISSUE:

User receive message "There was an error processing this request. Please refresh this page.", when trying add a comment to a News post.

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CAUSE:

The Comment feature is retired and is no longer available.

https://support.office.com/en-us/article/SharePoint-Online-Tags-Notes-feature-retired-77851BD5-6D5E-42FE-9BF6-D7C17EEB771F?ui=en-US\&rs=en-US\&ad=US

RESOLUTION:

Use Yammer, Groups or Open Graph Objects.

https://support.office.com/en-us/article/Embed-a-Yammer-feed-into-a-SharePoint-site-4817d2fa-50f6-4f25-88a0-a312745768d4?ui=en-US\&rs=en-US\&ad=US