Yes, you can change the Shopify product your Fan Pass is linked to.
However, if a customer has purchased the previously linked Shopify product but failed to claim it before the new Shopify product is linked, the ‘Claim Now’ button will not be present at checkout when they go to claim their Fan Pass.
Instead, you will have to regenerate their order by either manually creating a new order for the customer or creating a discount code for the customer to place the order themselves.