I'm on portal 8.5 with fixpack 9. I can access the webcontenthandler URL by browser and get the following response:  However, when I click the Get Libraries button, I get an error dialog with no information as shown below. 
I'm on portal 8.5 with fixpack 9. I can access the webcontenthandler URL by browser and get the following response:
However, when I click the Get Libraries button, I get an error dialog with no information as shown below.