To Run a PRI Debug:
Login as admin and go to Server > Advanced Debugging > Start a Debugging Session > PRI/BRI Debug:
Duration [enter time duration, usually in minutes]
Span [leave at default, if unsure]
Set Intense Logging On
Click on Begin Debugging Session
Note: It is best to run the Debug for only as long as necessary to capture the problem. The longer it is run, the larger the file becomes.
If you have more than one span on the PRI and don't know which span to select, refer to this article:
What span do I select when Running a PRI/BRI Debug?