After migrating our site to SPO, all of the lists when I try to open in Nintex Forms Designer, give an error of "Undefined" and then the page locks up preventing editing the forms in question. Here is the error presented by the Dev console, any help is appreciate:
NF.Infrastructure.Server failed. Unable to parse JSON for server response. responseText: <?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Request Error</title>
<style>BODY { color: #000000; background-color: white; font-family: Verdana; margin-left: 0px; margin-top: 0px; } #content { margin-left: 30px; font-size: .70em; padding-bottom: 2em; } A:link { color: #336699; font-weight: bold; text-decoration: underline; } A:visited { color: #6699cc; font-weight: bold; text-decoration: underline; } A:active { color: #336699; font-weight: bold; text-decoration: underline; } .heading1 { background-color: #003366; border-bottom: #336699 6px solid; color: #ffffff; font-family: Tahoma; font-size: 26px; font-weight: normal;margin: 0em 0em 10px -20px; padding-bottom: 8px; padding-left: 30px;padding-top: 16px;} pre { font-size:small; background-color: #e5e5cc; padding: 5px; font-family: Courier New; margin-top: 0px; border: 1px #f0f0e0 solid; white-space: pre-wrap; white-space: -pre-wrap; word-wrap: break-word; } table { border-collapse: collapse; border-spacing: 0px; font-family: Verdana;} table th { border-right: 2px white solid; border-bottom: 2px white solid; font-weight: bold; background-color: #cecf9c;} table td { border-right: 2px white solid; border-bottom: 2px white solid; background-color: #e5e5cc;}</style>
</head>
<body>
<div id="content">
<p class="heading1">Request Error</p>
<p>The server encountered an error processing the request. The exception message is 'Object reference not set to an instance of an object.'. See server logs for more details. The exception stack trace is: </p>
<p> at Nintex.Forms.Responsive.ResponsiveFormConverter.ToPixelPerfect(ResponsiveForm responsiveForm, Form formSettings) in D:a1sFormsCoreNintex.FormsResponsiveResponsiveFormConverter.cs:line 31
at Nintex.Forms.SharePoint.Services.ResponsiveDesignerServices.GetFormCanvasDataResp(ResponsiveForm responsiveForm, Form formSettings, String activityType, IList`1 fieldListCollection, String token) in D:a1sO365Nintex.Forms.SharePointServicesResponsiveDesignerServices.svc.cs:line 121
at SyncInvokeGetFormCanvasDataResp(Object , Objectt] , Objectt] )
at System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke(Object instance, Objectt] inputs, Objectt]& outputs)
at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc& rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc& rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage31(MessageRpc& rpc)
at System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)</p>
</div>
</body>
</html>
(anonymous) @ Nintex.Forms.SharePoint.min.js?v=JCaqjdV5YVCNhqBCQeYd6MV76RD9oveeAp4kXuJS1ek1:45136
c @ jquery-1.10.2.min.js:4
fireWith @ jquery-1.10.2.min.js:4
k @ jquery-1.10.2.min.js:6
r @ jquery-1.10.2.min.js:6
t @ zone.min.js:1
e.invokeTask @ zone.min.js:1
t.runTask @ zone.min.js:1
invoke @ zone.min.js:1
zone.min.js:1 Uncaught SyntaxError: Unexpected token o in JSON at position 1
at JSON.parse (<anonymous>)
at u.onMessage (nCaf.Library.min.js?v=iNIz47k8ykYHRB-L78wHf-7x41ZSCjcooQHrxD5namY1:1:56202)
at e.invokeTask (zone.min.js:1:16940)
at t.runTask (zone.min.js:1:13742)
at invoke (zone.min.js:1:18080)