Fx-portal: contract that inherits from FxBaseChildTunnel does not show up on PolygonScan as ERC721

I have a simple ERC721 contract that I want to use on Polygon to mint NFTs. Users will initiate mint with our DApp on Ethereum, which then uses fx-portal to to send a message to Polygon where the ERC721 contract lives and the mint and the NFT will live on Polygon.

The issue I’m having is that the Polygon ERC721 contract does not seem to be considered an ERC721 . This is most evident on Polygon scan, where the contract does not appear as ERC721.

I created a similar, Polygon-only version of the ERC721 contract (so does not inherit from FxBaseChildTunnel) and put that on Mumbai and it does register as an ERC721. This clue leads me to think that somehow inheriting from fx-portal is causing the issue.

The problematic, fx-portal dervied contract + code (it is verified) can be seen at: https://mumbai.polygonscan.com/address/0xc8224b52ae3c5a466262cd5822b302a579a7ef16#code

The version that does not use fx-portal and successfully appears as ERC721 can be seen at: https://mumbai.polygonscan.com/address/0x0CE2E3bCebBd1cBeB8D3f6588a7E77f89DAB29F8#code , in this case you can see the “Token Tracker” exists and you can see the token I created

you can see that the events look right in both cases.

why is this happening? how can i get my fx-portal child class to also register as ERC721 ?

thanks for your consideration and help.