Hey there, @jpalacios!
Ryder here, from the Social Care Team at Shopify. Thanks for posting! I'm sorry to hear about this error your customers are seeing. Often this error will display if your shipping settings or shipping profiles don't match the products in the cart. Have you confirmed they're located where your shipping profiles are setup, and that your products meet the pricing or weight ranges?
I've attempted to checkout, however I'm located in Canada and not sure if your rates are set for Canada currently. I'm also unsure whether your products are set to meet the weight/pricing ranges of your Shipping Settings. I'd be happy to take a deeper look into your Shipping Settings and escalate if necessary. I've gone ahead and sent you an email to the email address associated to your Community Forums account. In order to authenticate you and access your account, can I please have you respond from the email address associated to your store? If you're using a separate email address for you store, you can simply CC the correct one and respond through there.
Looking forward to hearing from you soon!