Scheduled system flow stopped working

I just had an issue with the scheduled system flow that was perfectly handled with a TCP call by ​@Angelica van der Beek . 

I thought it would be worthwhile to share it in the community, in case someone else encounters the same issue. 

At our customer we had a systemflow scheduled every 5 seconds, in order to treat incoming calls. 

The system flow did not work, wh in the production environment while in Acceptance it did. We did verify all settings according to documentation:

 

- Configuring pool users

https://docs.thinkwisesoftware.com/docs/deployment/indicium#configuring-pool-users

- Create the web application

https://docs.thinkwisesoftware.com/docs/deployment/indicium#create-the-web-application

- Restarting the application

https://docs.thinkwisesoftware.com/docs/deployment/iis#restarting-the-application

- application Initialization

https://docs.thinkwisesoftware.com/docs/deployment/iis#application-initialization