Options will depend on method of payment perhaps. If you paid by credit card, then you might be able to get a refund by showing the communication thread.
Six weeks is generally a long time to wait to get an order from just about any where in the world these days - not excluding the international disruptions going on. Exceptions are out there like Print-On-Demand and other back logs and sometimes a supplier has to wait for materials to arrive. But if that is the case, they should be letting you know.
Given the printing world, perhaps the items are actually printed in China and might be stuck in one of the literally hundreds of thousands of containers that aren't 'flowing through the supply chain'.
Maybe try another email (if not already done) commiserating with the supplier about the overall situation vis-a-viz the tariff chaos, and asking them straight on if that is causing the delay and asking for your options regarding waiting or a refund.
If no answer to that email, I'd chase the refund option. But I'd give it at least a week for an answer.