Due to BTC exchange rate fluctuations, the payment may be minimally too low to cover the price by the time it reaches MFP. This happens especially when you make the payment through an exchange such as "Binance". Exchanges take a little longer to accept payouts, so the small difference may occur during this time. In this case, report the case to the support (support@myfirstplant.eu) and provide them with the order number and TX hash of the BTC transaction.