PLEX Hauppauge tuner not found

I run flex on a windows platform and i installed an hauppauge USB tuner that is in the list of supported devices.
WINTV is working fine and i can tune to channels, but PLEX is not finding the USB tuner.
Im running Version 1.5.5.3634.

what could be wrong?

The latest Plexpass version of Plex is required for USB tuner support

Your server is too old. You need 1.7.3
Settings- Server- General - Show Advanced - ‘update channel’ = ‘Plex Pass’