I've searched the web for your inquiry and it appears that you have to contact the local reseller of UPSMON or the one from where you've acquired the devices to ask them about the PRTK code. There are many users online who have the same issue as you.
It's said that the PRTK code is printed on the UPS Data label, but no one can find it. Their website doesn't provide anything in terms of PRTK information. There is a button on the page, but it does nothing(linking, downloads, troubleshooting, etc).