New subscribers not emailed

Your software
My Mautic version is: 2.16.2
My PHP version is: 7.2.24-0ubuntu0.18.04.6

Your problem
My problem is:
Our email sending has been drastically reduced since upgrading to 2.16.2
I’m trying to track down exactly what is happening but so far haven’t nailed it down. It appears that the campaigns early in our sequences have stopped sending since the upgrade but later campaigns are still sending.
We were averaging 3500 sends per day and we’re now averaging 400.

These errors are showing in the log: mautic.EMERGENCY: lead not found

That error was there before the upgrade. Have not been able to figure it out. The error shows about every 10 seconds

So it appears that all users that were previous to the upgrade are flowing through the campaigns properly. Users added after the upgrade are not. all actions for new subscribers are showing as pending