So I used 75g MHRB in 2 37.5g batches. I extracted with Naphtha and have a pint jar of it. I froze it for 9 hours and there is no sign of precipitation. Any advice?

Naphtha is too strong of a solvent for freeze crystallization, that is why aliphatic solvents like heptane and 50-70º petroleum ether are normally used. In heptane DMT is so poorly soluble that the solvent needs to be warm just to dissolve it and then, after 24-72 hours in the freezer, nearly all DMT crystallizes out. Solvents like naphtha or xylene dont work like that.
You did as I would, you did the initial extraction in a more 'friendly' solvent. Now you can extract it into acidic water, base the water layer, and a] extract it with warm heptane and freeze precip the heptane layer or b] extract with a minimal amount of toluene or naphtha and try to evaporate the solvent.
There are many teks here, read several so you can adapt to available materials and methods practical to you.

CYB's max ion tek suggests evaporating light naphtha by about 40%, or until it becomes cloudy with precipitation at room temperature, and then freezing to form crystals. Obviously the 40% may not apply if you used a substantially different solvent:root-bark ratio. Heptane is suggested for re-crystallization.

Tek is here: Max Ion Tek

Naphtha works fine, just evaporate until supersaturated. Precipitation can occur at room temp.

While your naphtha may be different and contain significant quantities of aromatic components, in my experience as long as it contains, principally, aliphatic hydrocarbons - and little to zero in the way of aromatics - it will precipitate just fine in the freezer.

JMelbrook17, if you have a pint (476mL) of naphtha from pulling 75g of bark it's little wonder there's nothing precipitating. As an alternative to wasting solvent and polluting the atmosphere by evaporating your naphtha, performing a mini A/B by backsalting into vinegar, adding base, then pulling again with far smaller volumes of naphtha will also do the trick.

Considering that from the amount of bark you've used, 1.5g of DMT might be considered an excellent yield; therefore the maximum amount of 5% acidity vinegar you would need to use to wash your naphtha will be: (60/188)*1.5*(100/5)= just under 10mL. Clearly a larger volume would be slightly easier to handle so you can dilute this with distilled or deionised water.

Of course, there's always a possibility that your extraction was unsuccessful but without further details it's harder to pinpoint any problem. That said, the two likely problems are poor technique or bunk bark.