Why can't I pay an Ethereum Invoice using MetaMask in Firefox?

There are several wallets which are compatible with BitPay’s invoices. Which wallets work for a BitPay invoice?

However, BitPay invoices are unable to support MetaMask in Firefox at this time. This is due to how MetaMask is implemented in Firefox, combined with browser Content Security Policy blocking inline javascript. We are exploring alternative solutions to allow compatibility. However, our current recommendation is to use MetaMask in Chrome when paying a BitPay invoice.

There is an open issue for this on the MetaMask github page. We recommend adding feedback there to tell the developers about this issue.