We just updated Nintex Forms from 2.9.2.0 to 2.11.5.30. After the update some of our forms won't Print To PDF. On some of our forms the feature works fine but on others it comes up and says "Converting to PDF..." for a brief time and then that goes away but nothing happens. In Chrome we get the same message but it doesn't go away and nothing else happens.
I reviewed the ULS logs and found the following error: "Unable to convert to pdf. System.Exception: HTML load error. Unknown network error at Winnovative.HtmlToImageConverter"
And "Application error when access /_layouts/15/nintexforms/PrintPdf.aspx, Error=Object reference not set to an instance of an object. at Nintex.Forms.SharePoint.ApplicationPages.PrintPdf.ProcessPdfResponse"
I've seen some other similar posts but the answers didn't seem to help. There are no background images on the form, I have tried removing all custom JS and CSS from the form, I have checked the "Replace a process level token" policy in Local Security Policies to make sure the Application Pool users are listed.
Can anyone think of any other possible causes for this?