Can I create nexus if I sell on a marketplace?

It depends. Some states require you to register if you sell via Fulfillment by Amazon (FBA), others count FBA sales toward economic nexus thresholds. Additional states have marketplace facilitator laws in place, requiring marketplaces to collect and remit sales tax on behalf of sellers. And if you sell through multiple channels, you may still trigger nexus and be required to register and remit on your own, even in states that collect from marketplaces.