WordPress Error on facebook page

Hi, I encountered error while autoposting to facebook from a subdirectory. I use accesspress plugin to post to facebook both on root and subdirectory. On the root directory, there is no problem at all but with the subdirectory, I keep getting ‘WordPress error’ on facebook post. How do I solve this problem?
My permalink setting is set to default ‘plain’
On facebook, the link to the post shows but without image. Instead WordPress Error is displayed. When I click on it, it takes me to the post on the site.

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