Configure Popup Window is blank
I am having some issues trying to configure my popup for a simple 1:M relate. I can enable them, and the Configure window opens (as shown in attachment), but none of the fields will populate to let me configure them. On top of that, at this point, I can't hit OK or CANCEL, I have to refresh the browser and start over.
I thought it might be my data, i.e. duplicates in the join field, etc. But I created a test dataset with just a few records and got the same result. I have also tried publishing from both a file geodatabase and an enterprise geodatabase.
And lastly, I know the relate works, because the Show Related Records to open the table at the bottom works.
Setup:
SignsSupport feature class
Signs relationship class
Signs table
ArcMap 10.3.1
ArcServer 10.5.1
Thanks in advance 
