I wanted to dabble in making dairy-free kefir, whilst keeping the caloric content on the low end. I planned on using Unsweetened Almond/Coconut Milk to match my goals.
Will the lack of sugars/lactose/I'm not sure what else make it an un-kerif-able mix?
Kefir grains need sugar to live; otherwise they starve. Dairy kefir grains specifically need lactose, so I would suggest water grains, unless you want to give your dairy grains a milk bath every few days for at least 24 hours to recover. Dairy grains will ferment coconut milk (I have done this, swapping with dairy milk to keep it happy), but will not thrive in it.
Are you using boxed milks with very little native sugar? If you find the grains are struggling, Adding a little sugar to the coconut or almond milk will help feed them; your calories won't increase much because the bacteria consume the sugar.
From my experience, Milk kefir grains should be cultured in dairy milk. It's possible to do half almond milk and half raw milk and still get results, but you risk weakening the culture. Plus, Almond Breeze has several non "paleo-friendly" ingredients. You could try making your own almond milk if you're totally against real milk. If you choose to try and add a sugar, steer clear of honey - it's antibacterial properties could also damage the balance. If you want to further reduce the lactose content (carbs, sugar, calories) of milk kefir, you could do a second ferment, but I would only feel comfortable recommending this with raw milk.