Mixing on SubZero SZ-MIX04

Good afternoon; just joined this forum, and have found some great ideas! I hope my query below is acceptable via the rules?
I have an issue with my Christmas present, SubZero SZ-MIX04; the idea is to not annoy my wife and neighbours. My plan was to have two inputs (1) cable from laptop into the MIX04 and (2) standard jack cable from bass guitar PHONES socket into the MIX-04 LINE/IN socket, then attach headphones to the PHONES output socket on the MIX-04. That way, I can "play along" to songs, with the ability to adjust the bass and the song EQ.
However, the laptop music comes through fine via a 3.5mm cable from laptop socket to red and white cable inputs on the 2TK/IN sockets; but, I cannot get a signal from the 6.3mm cable from the bass PHONES socket to the LINE/IN socket on the mixer. Tried stereo 6.3mm cables but no joy.
GEAR4 who I bought from have been helpful, but only suggest now it could be cabling?
Any suggestions? Thank you!!
I have an issue with my Christmas present, SubZero SZ-MIX04; the idea is to not annoy my wife and neighbours. My plan was to have two inputs (1) cable from laptop into the MIX04 and (2) standard jack cable from bass guitar PHONES socket into the MIX-04 LINE/IN socket, then attach headphones to the PHONES output socket on the MIX-04. That way, I can "play along" to songs, with the ability to adjust the bass and the song EQ.
However, the laptop music comes through fine via a 3.5mm cable from laptop socket to red and white cable inputs on the 2TK/IN sockets; but, I cannot get a signal from the 6.3mm cable from the bass PHONES socket to the LINE/IN socket on the mixer. Tried stereo 6.3mm cables but no joy.
GEAR4 who I bought from have been helpful, but only suggest now it could be cabling?
Any suggestions? Thank you!!