My card reader says I'm in TESTMODE ONLY, how do I fix this?

This error means your Stripe account isn't set up for card-present (EMV) transactions yet:

The card_present source type can only be used in testmode

Stripe often starts accounts with this turned off. To turn it on, contact Stripe's support team:

https://support.stripe.com/email

Let them know:

1. You're using a Stripe Terminal card reader with Payment for Stripe (a Stripe Premier Partner)
2. You want to process EMV transactions, but your account is in the testmode_only state
3. You can't process EMV transactions until they allow them in live mode