Facebook Feed stop working

Hello,

Today, I found a problem about the facebook feed stop working.
I uesed the Flow-Flow Social Stream Lite v. 3.1.66.
This is the message alert on my front page, please see https://prnt.sc/v3s888

And I try to check the settings of Admin Area that alert message;
Plugin received next error message from network API for this feed:
(#100) Pages Public Content Access requires either app secret proof or an app token.

So I try to check my Facebook App but no error and I try to Access Token Debugger but still not working.
How to fix it?
Please advised.

Thank you,
Thananit

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