Multi Server setup, updated Master server from Ubuntu 16.04 to 20.04 and it crashed

So to try to make a long story somewhat shorter.
I have a multi server setup. My master server has been on Ubuntu 16.04 for the longest of time because I didn't want things to crash. As 16.04 is now no longer supported I decided to bite the bullet and upgrade the OS. I took it to 18.04 and it all seemed to be doing OK. Then I took it to 20.04 and it no longer was doing so good. My slave servers was no longer able to connect to the Master server. I backed up the dbispconfig database and the mysql.user database and table. I did a fresh install of 20.04 and uploaded the databases to the new setup. After many hours, I have the Master server back up and running. However the slave servers are not getting the changes applied to them when I make changes in the Master server. I am able to run the update script on the slave servers and they all see and connect to the Master server. I don't see any error messages in any logs. I have run the test script on both Master and some of the Slave servers and I can't find any issues.
I am at my wits end here not able to find where the issue is. The Master server doesn't put anything in the queue when I try to make changes to the the slave servers but if I try to make a change to the Master server I see the number for changes in the queue on the top of the dashboard.

Test script gives the below results.

I put ISPconfig in debug mode and still no issues that I can locate. If anyone know how to get the Master server to push the cron jobs to the slave servers that would be great. I did reinstall ispconfig per the Perfect Server instructions and then I uploaded the old database backup.

 

Thanks Till for pointing me in the right direction. Ran ./server.sh and got the following error on one of my slave servers.
01.06.2022-10:43 - WARNING - There is already a lockfile set, but no process running with this pid (3624754). Continuing.
Datenbank nicht gefunden / Database not found PHP Fatal error: Uncaught Error: Call to a member function testConnection() on bool in /usr/local/ispconfig/server/server.php:64
Stack trace:
#0 {main}
thrown in /usr/local/ispconfig/server/server.php on line 64

 

php 7.4.3

 

So that is on one of my web servers (have two)
On my database server I looked at the cron.log and found this information.

I have looked at the logs and can't find the issue other than what is showing here.
I still think that my ispconfig master server isn't creating the jobs for the other servers to process. It won't give me any queue if I create anything for one of the slave servers. I don't get any issues when I run an update.php on the slave servers. It all goes through.