As part of the verification process for PICKitPlus we verify against the PICKit4 - however, the PIckit4 programmer is failing to program the 18FxxQ71 range.
Just had this confirmed by Microchip.
The colleagues from the relevant business unit confirmed the issue, but, unfortunately, there
is no workaround for now. It will be fixed in the next MPLAB version, 6.10,
possibly to be released in the next quarter. Until then, maybe you could
continue working on your project using the PICkitPlus programmer, if you are
able to program the microcontroller with this tool.
Thank you for reporting this issue to us.