Something else that might be causing issues is that your username is uppercase in the JSON file.
the NIP-05 spec says the name part of "name@domain.com" is case insensitive, but it dose not say anything about the JSON file.
If you look at https://nostr-check.com/.well-known/nostr.json all the names are lower case. I dont know if it will fix it but it cant hurt to copy what everyone else is doing.