Facebook auth codes expiring?

Thanks for this amazing plugin!

There’s just one thing that’s driving me crazy: after I enter all my FB auth codes, everything works perfectly. But after a short while (couple of hours, maybe half a day) it stops working and I get the ‘400 Bad Request’ issue.
Meanwhile, the Twitter stream keeps updating just fine.

When I get new auth codes from Facebook (by adding a new app) it works fine again – for a couple of hours. Only way to reactivate is by requesting new codes. This can’t be the way it should be, can it?
So what’s happening? Do the codes expire? Am I missing something?

Hope you can help, TIA.

https://www.ads-software.com/plugins/flow-flow-social-streams/