[cups] Printer added to windows 10 client appearing as unspecified device

[Steve Root]

Situation:
I have an IPP enabled printer
I have CUPS 2.2.12 running on ubuntu 19.10
I have added the IPP printer to CUPS and can print a test page.
I have shared the CUPS queue to the network, and from a windows 10 client I
can view and add the printer.

Problem:
When the printer is added, it gets listed as an 'unspecified device' and
not a printer (screenshot attached).

[note for future readers: no failure or error is shown on the windows 10
client. If using the newer windows add printer interface, after adding the
printer will not appear in the list of printers then when searching/adding
printer again, this printer will no longer be visible as an option to add.
I discovered it was added as an unspecified device by using the old style
-> "Control Panel\Hardware and Sound\Devices and Printers" view]

There were no errors in the cups log so I've turned on debugging in the but
I still can't see anything that looks odd. It looks like the windows 10
client searches for printers and cups replies, but when a particular
printer is added Windows 10 doesn't need to ask for any more information.
For what it's worth, here are some of the lines (10.18.6.55 is the server,
10.18.6.21 is the client).

D [09/Nov/2019:10:35:32 +0000] [Client 26] POST
/printers/kyocera_faxprintscan_m2535dn HTTP/1.1
D [09/Nov/2019:10:35:32 +0000] Get-Printer-Attributes ipps://
10.18.6.55:631/printers/kyocera_faxprintscan_m2535dn
D [09/Nov/2019:10:35:32 +0000] [Client 26] Returning IPP successful-ok for
Get-Printer-Attributes (ipps://
10.18.6.55:631/printers/kyocera_faxprintscan_m2535dn) from 10.18.6.21.

If anyone has any suggestions or pointers on how I can resolve this I'd be
most grateful

Thanks
Steve