That version is outdated. Please update your system with the package manager apt.
You did not really install that 3 year old version. You would not have DVR support. This was added much later. The important package is plexmediaserver-installer, not plexmediaserver. The last one has been empty for years 
Raspbian Stretch is perfect. Please review my official instructions and make sure you did something like this to install PMS:
Then you did fetch the wrong firmware. Please take a look at the following link to get the correct firmware and then compare your kernel logs with the logs in following link. Last remark: you will only have access to one tuner. Hauppauge just pushed the support to the second tuner to upstream Linux 4.17.
https://www.linuxtv.org/wiki/index.php/Hauppauge_WinTV-dualHD#Firmware
