Tax a non shippable product?

I searched the forum and didn't find much, I'm using 4.60.6 and I need to tax non shippable products, i.e. software licenses for one state (due to nexus). I tried changing config/tax settings from shipping to billable address (and default as well) and nothing is working. I set a tax category on the product for this tax which is configured for one state in the US and the tax rate. Yet at checkout no tax is applied.

Any suggestions?

Also, on another note, I don't see any place for a customer to set a default address. Can someone explain that option as seen in the tax address option?

I've not actually just tried it, but I'd think that tax should work for non-shippable providers if you have tax settings set to billable address or default.  (Although I'd need to look at code to see what it would do if it was set to use shipping address and there is no shipping address on the order ;)

Check if the customer role or the product is marked as tax exempt.

RE: "I don't see any place for a customer to set a default address. "
There is none. It would require customization.
I believe that the fields in the Customer table (in DB)
      ,[BillingAddress_Id]
      ,[ShippingAddress_Id]
are just used (temporarily) during the checkout flow.

RE: "Can someone explain that option as seen in the tax address option?"
On the Admin Tax Setting page there is a
    Default tax address (used for tax calculation)
Selecting the "Tax based on" setting to "Default address" will force it to use that address.