You have this at the top of your page
To pay with altcoins such as Dash, Zcash, and others, the invoice amount must have a converted value of 0.001 BTC or more. Invoices below 0.001 BTC cannot be paid with altcoins.
But I get this if I try to pay with other coins below that amount it does work:
I did not pay since I don't know if you have anything to stop it on the back end. But CoinGate is letting people pay, and you don't honor it then you are going to have issues.If CoinGate is not blocking the lower payments when they should that is between you and them.
I actually just paid with LTC and it let it though.
Side note a $5.00 card sold for $5.70 so you
really have to check your rates.
-Dave