Hi Jaynehughes,
Welcome to the eForum!
I believe this is due to the difference in pricing, your old model did not have an expiry date on the credit however the new rev version will expire after 30 days so I think your SIM has confused the dongle as it is not designed for the credit that does not expire.
We no longer sell the older models so my advice would be to try and buy one of the older K3565 models from a third party and then your SIM would work fine. The new K3565r would need to be topped up with its own SIM card and the £15 for 3GB offer is only valid for 30 days before it expires and you would need to TopUp again.
If you need anymore help with this let us know.
Thanks
Holly
eForum Team