Probably to cold. Either get a heat belt, or move it somewhere warm. Depending on the yeast, you typically want it around 22-26°C. I like to pitch around 28 so it gets a good start, then let the temp come down a bit before using a heat belt. It won't have anything to do with headroom, as long as your fermenter is sealed you should see bubbles.
Also, get a hydrometer! You have no idea what is going on without one. If your sugars were to low at the start, you won't have enough to kickstart fermentation. Take a measurement. If it is below 1.030 I'd be adding a bunch of sugars. There are tools to calculate how much to get the gravity where you need it.
When you get this warmed up, I'd re-pitch more yeast as well. It's not likely, but possible you got dead yeast. No real harm in pitching more, that I know of anyway.
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