how did secular rulers challenged papacy authority?

Hi!

With the inclusion of secular rulers, the papal did face some challenges. These secular rulers campaigned with an anti-papal message, which did present challenges for the Pope.

Secular rulers also established a General Council which worked towards monitoring the Pope's actions, and stepping in when necessary. 

Hopefully, this helps! =)

In the 14th and 15th centuries, secular rulers challenged papal authority through an anti-papal campaign (Unam Sanctum) and installing a General Council to regulate the Pope's actions.