When you open a simple scheduler demo from scheduler-pro screen, then click on the header of hte demo, you navigate to wrong URL and see 403.
Go to https://bryntum.com/products/schedulerpro/examples-scheduler/workingtime/
Then click on the "Working time demo" title at the top bar.
You are taken to: https://bryntum.com/products/schedulerpro/examples-scheduler/#example-examples-scheduler-workingtime