Why doesn't the Callback work for the payment on the mobile platform?

Question

Classmates

Callback does not work in our application for the payment on the mobile platform?
The function works on the PC, but on the m.ok.ru mobile platform it stopped working some time ago (1-2 months).
We actually use the same code and fapi5.js What to do?
function API_callback(method, result, data) - not working. on mobile.
The game “Find a Phrase”
https://ok.ru/game/wordsfind - PC payments work
https://m.ok.ru/game/wordsfindmob - Mobile payments do not work. And even when you run the mobile version on the PC, the payment callback does not work.