DKIM Verification Failed

DKIM Verification Failed

I am having a problem getting DKIM to verify my domain. I'm getting the "verification failed" message. I created a TXT record at my domain DNS manager a few days ago but it's still not verifying. I guess I am doing something wrong although I can see others on these forums experience this and it's sometimes required a manual verification? Please can you advise me on how to resolve this issue?

Thanks, Al.