iqaudio pi-dac+ not visible

Installed volumio 1.55 on raspberry pi B+ (not 2) and iqaudio pi-dac +. Activated the driver and rebooted but only alsa available as playback device. Music can be heard from onboard jack, but nothing through dac + outputs. On connecting with putty and running alsamixer the dac+ is not available to be selected as soundcard. Any ideas to get the driver working properly?

Worked fine with my Pi2 with IQaudIO Pi-DAC+ and it is working perfectly. I did activated the I2S driver and selected IQaudIO from the playback selection. Is the DAC seated correctly on the header?

Hi Tristran
I think so - power led is on. Even after I have activated driver and rebooted the dac+ is not visible in the playback device menu - can only see ‘Alsa’.