Why can't the payment be displayed?

Question

Classmates

Good afternoon!
I call FAPI.UI.showPayment
(n, d, c, price, null, null, "ok", "true", null); where n - product name ("10 bars"), d - empty string, c - code (" gold_pack_1
"), price - price (75)
part shows the message "Payment system on maintenance..."
There are no errors in the console. The application's callback URL is full, but it's not receiving any requests.
What could be wrong?