I paired mine to a win10 PC, which worked fine. Trying to pair to a second win 10 PC at work, I get the exact same thing as reported in the OP. I don't even get offered installing the certificate. Has anyone found a workaround yet? I just want to be able to print to the RP1 at work.
Edit: I managed to connect mine following
troubleshooting advice by Sony for Win7 PC's on their forum. I did things
slightly differently, but basically the same:
(1) Unplugged USB cable from the DPT
(2) Uninstalled the Digital Paper app
(3) Checked if I needed to delete "C:\Users\(User Name)\AppData\Roaming\Sony Corporation\Digital Paper App" (was already deleted)
(4) Rebooted
(5) Quit all unnecessary applications (I also killed an AnyConnect related process in the task manager, probably not needed)
(6) unplugged from network to be safe (don't like running without the firewall active, probably paranoid..), disabled firewall, disabled real time scanning for Defender
(7) Installed the Digital Paper app
(8) Rebooted
(9) Started the Digital Paper app
(10) Plugged in DPT to USB port directly on the laptop (not in any USB hubs or USB ports on my monitor). This time Digital Paper App successfully detected the DPT, and I was asked to install the certificate
(11) Re-enabled the firewall, re-enabled real time scanning in Defender