Someone sent me tokens on another network and they have not arrived

Your address is the same on Polygon, Ethereum and BNB Smart Chain, but each network keeps its own balances. Tokens sent on Ethereum are in your Ethereum balance, not your Polygon one. Switch networks on the Wallet tab to see them.

That is why the Receive screen says Send only [network] assets to this address. Moving tokens from one network to another needs a bridge service. The app cannot do that, and support cannot do it for you.