Attestation of new external users

Hello,

I want a person to approve new external users, but if some time pass (for example, 30 minutes), I want to approve this attestation automatically. 

I configure the parameter "Timeout (working hours)" in the approval level (in Manager) to 30 minutes and I have done the following tests:

   - On monday, I have created 2 new external users (at 18:38 the first user and at 18:48 the second user).

   - Today (wednesday), I have created a new user at 9:40. 

I see in the Manager that the first 2 users were approved at the same time (on monday, at 19:22) and the user that I created today, has not yet been approved.

This is not  normal, the time to approve automatically does not work correctly. What is the cause? I think that it is a process that runs only once a day for approve automatically. 

Thank you, 

Regards.