Failed to tune error when scanning a mux

Hi,

I just bought myself an RPi Model 3b+ and installed LibreELEC on it. I also had a MyGica T230C stick lying around, so I decided to set it up with TVHeadend on the RPi.

However, when I add a mux, I get this error in TVHeadend's log:

2019-01-16 08:28:39.520 mpegts: 306MHz in ISPName - tuning on Silicon Labs Si2168 #0 : DVB-C #0
2019-01-16 08:28:39.520 linuxdvb: Silicon Labs Si2168 #0 : DVB-C #0 - failed to tune [e=Invalid argument]

What could be causing this? I tried to debug using w_scan, but that returns a helpful error

main:4007: FATAL: ***** NO USEABLE CABLE CARD FOUND. *****
Please check wether dvb driver is loaded and
verify that no dvb application (i.e. vdr) is running.

Any help would be appreciated. Thanks!