Interaction with metamask app not working

Hello, my dapp works correctly with desktop browsers.
It uses Web3Modal together with @metamask/detect-provider to show popup and use metamask.
this is a piece of example

let res1={ERC20CONTRACT}.methods.approve(this.rft_addr,amount).send({from:maddress,type:type}).then(async ()=>{
}).catch((err) => { alert(‘ERROR’) });

it works perfectly on desktop browser: the metamask plugin appears, I confirm the approval, then alert SUCCESS appears on the screen.
Same code stop working on mobile browser when interacts with metamask app. The metamask app opens, I confirm on approval, but nothing happens on my website. No error, no success message.
What’s missing? thank you