Following router replacement on a small network, a customer reported 3 weeks after installation that the printer was not connecting to the Instant Ink service. This had previously worked fine.
The printer was printing from the email service okay and the internet connection seemed okay
Online searches revealed possibilities including printer date time, DNS settings on the printer and perhaps a need for firewall ports to be configured. None of these appeared to be the issue, since they were unchanged from the previous working configuration.
Following further diagnostics and network packet capture, I found the the printer connections to the Instant Ink service were not reaching the WAN since the packets were set not to fragment, and were being rejected by the router.
Once this was discovered, I determined the highest MTU value that allowed connection to Instant Ink, tweaked the MTU value in the router to match and Instant Ink service connections were restored (i.e. reduced the MTU value slightly from the specified value). No firewall rules needed.
This seems to be a solution that I've not found documented online.
I accept that this was probably a misconfiguration of the router MTU, but I suspect that many people installing a new router would not change the default value.
Has anyone else discovered an issue with fragmented packets preventing connection to Instant Ink?
@Shlomi The printer is connected to a wireless network, I first tried another wireless network from a mobile hotspot and since that connected okay, it showed that it was some issue with the local network and not the printer.
I am convinced that the problem was packet fragmentation but just surprised that I've not seen that mentioned anywhere.
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