Why I am being charged sales tax when previous orders were tax-free?

Due to a recent Supreme Court decision [South Dakota v. Wayfair, Inc. June 21, 2018], states may transfer the burden of tax collection to vendors even if the vendor does not have a physical presence in the taxing jurisdiction. Therefore, to be fully compliant with the various state laws, we must collect sales tax in all states that have chosen to enact remote sales tax laws..