This was a Bug and it has been fixed in recent deployments. Though to get "Submit Button" working on your portal, you need to save it again in cmx cloud portal library. Please follow following steps to fix issue with submit button.
Step 1: Go to Connect& Engage
Step 2: Go to Library-->Portals
Step 3: Select your portal" which you have assigned to Site
Step 4: Save the Portal" by clicking the save Button.
Step 5: Connect to SSID
Step 6: Open IE Browser and Check the portal .
Note: Try to save the portal only from Library option under CMX experiences, otherwise the portal save changes will not get reflected in Cloud.
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