Please not that there is a timeout issue with the Qlik Rest connector if you expect receiving data from the API sources after 5 minutes. Even if you apply the maximum timeout setting of 10000 seconds you might get the following error message (in Qlik Sense November 2020 and older versions):
At the same time if you compare with the POSTMAN API tool, you might see that there is no error when you get the data after 5 minutes of timeout from the REST API source:
Environment
Qlik Sense November 2020 and older
Cause
The issue was caused by a product Defect ID: QB-2445
Resolution:
In order to solve the issue you would need to upgrade to Qlik Sense February 2021.