We're seeing a lot of issues relating to this as well - started around 6:30pm on 7th August but escalated today as customers on our apps are processing payroll. Started off returning a large number of "invalid_grant" errors, and as customers have re-authenticated we've started seeing "The supplied OAuth token (Bearer) is not valid" instead.
We're investigating app code changes to try and mitigate this/determine any latent issues in our authentication. tanvir are there any further updates on why this has started happening recently/what changes are occurring in the identity services?