The reason you are not seeing your domains in the collectibles section of your wallet is because wallets have not yet integrated NFTs minted on the Polygon network.
Keep in mind, once a domain is minted you will be able to view the transaction in the Polygon block explorer. A successful transaction means that the domain has successfully been minted to your wallet.
Another way to view the Web3 Domains is by viewing your Profile on OpenSea. Please follow the steps below to view domains minted on L2 (Polygon):
Click on the wallet icon at the top-right corner of the menu on OpenSea and select the wallet you have minted the domains to.
After connecting the wallet, hover the cursor over the identicon and click on Profile.
You will view the domains you have minted in the Profile section. Domains minted to the Ethereum and Polygon networks will display side by side.