Error creating access token - which app?

Hi for last 2 days 've been getting ‘Error creating access token, have you ENABLED OAuth in smart app settings’ - early every hour sometime 10 times in succession.
I have OAuth enabled in every smart app I use, I have refreshed the client secret in every SmartApp - twice!
Is there anything else I need to do ? or anything else I can do to troubleshoot which app this is etc ?

Thanks for any ideas/assistance.

Where are you seeing this message?
Have you checked live logging to see what smart apps are logging issues?