I've noticed this on one of my machines as well. No solution here.

For these impacted computers, could you try running this command in terminal to verify that your computers are able to hit your Jamf Pro server?

sudo jamf checkJSSConnection

If your computers can properly see your Jamf Pro, it might just be the Self Service app unable to see it, at which time I'd recommend removing the app and re-issuing it out to your computers.

This worked! I deleted Self Service, then re-added with "sudo jamf policy" and then install then worked without incident.

Thanks!!

for me that doesn´t work.
i encountered the same problem with VPP Apps Pages and Keynote.
checkJSSConnection is ok.
re-adding Self Service doesn´t fix it.
Self Service Notification says:

I've seen this error in Self Service. I believe the solutions mentioned above are concidental and more about timing. The few computers that have presented the error, will begin working without any changes just by waiting 5 to 60 minutes. It appears to correlate to repeating messages within the JSS log concerning MDM, but that's my speculation. Log example:

2018-03-16 08:21:11,047 [error] [Tomcat-88  ] [MDMController            ] - Error processing mdm request, returning 400. Device: Null, CommandUUID: mraNull

2018-03-16 08:21:11,781 [error] [Tomcat-132 ] [JAXBPlistParser          ] - Error unmarshalling

2018-03-16 08:21:11,781 [error] [Tomcat-132 ] [MDMController            ] - Error processing mdm request, returning 400. Device: Null, CommandUUID: mraNull

2018-03-16 08:21:15,391 [error] [Tomcat-39  ] [JAXBPlistParser          ] - Error unmarshalling

2018-03-16 08:16:45,038 [WARN ] [duledPool-0] [pleMDMCheckInNotification] - Unable to create push notification for device: ComputerShell [ID=2570, Name=computernameabc]. A required field (UDID, APN Token, Push Magic) was empty.

2018-03-16 08:16:45,038 [WARN ] [duledPool-0] [pleMDMCheckInNotification] - Unable to create push notification for device: ComputerShell [ID=2516, Name=computername123]. A required field (UDID, APN Token, Push Magic) was empty.

2018-03-16 08:16:45,038 [WARN ] [duledPool-0] [pleMDMCheckInNotification] - Unable to create push notification for device: ComputerShell [ID=4203, Name=computernamedef]. A required field (UDID, APN Token, Push Magic) was empty.

2018-03-16 08:16:45,038 [WARN ] [duledPool-0] [pleMDMCheckInNotification] - Unable to create push notification for device: ComputerShell [ID=3755, Name=computername456]. A required field (UDID, APN Token, Push Magic) was empty.

2018-03-16 08:16:45,038 [WARN ] [duledPool-0] [pleMDMCheckInNotification] - Unable to create push notification for device: ComputerShell [ID=2839, Name=computernameghi]. A required field (UDID, APN Token, Push Magic) was empty.

what worked for me now is to use this:

#!/bin/sh

jamf removeMDMProfile -verbose

rm -rf /var/db/ConfigurationProfiles

sleep 20

jamf mdm -verbose

sleep 20

jamf manage -verbose

i found the script in this post.
i guess it must be something with the "MDM Capable Users" and the VPP App Store

We have got the same issue, But only with VPP apps which indicates that port 5223 can not be contacted, I am seeing a lot of Push Notification errors from the device.

Did we ever find a resolution to this? I checked JSS Connection and its fine. I re added Keynote to be installed through keynote using VPP and still I'm getting the same error. And when you click to install keynote it takes you to Keynote in the App store.

The problem for me was that the computer I was testing on was not enrolled into the Jamf MDM. I had the Jamf agent installed, so I could run policies, however the MDM profile was not enrolled. So for troubleshooting, try unenrolling and re-enrolling device into the MDM.