I hate to admit it but it's likely true that proofofbrain.io is defunct. There is probably a grace period with the registrar the site used but if @proofofbrainio didn't renew in time it's unlikely to be picked up soon.
There is proofofbrain.blog as a replacement, which is great, but it lacks certain features the original site had, such as the NFT section. Fortunately OpenHive can help keep the POB NFT market going from now on.
Shortly before proofofbrain.io closed down I minted some NFTs in a collection. Then, I minted the last NFT ever to be minted on proofofbrain.io.
Image Source: proofofbrain.io
I minted the last NFT on proofofbrain.io solely to own it. I purchased edition #1 of the first NFT minted on proofofbrain.io by @calumam, so owning both the first and last NFTs minted on the site bookends that small slice of Hive history.
I believe I made an appropriate choice. I tokenized the 3D model of a Proof of Brain token I created back in 2021.
Image Source: proofofbrain.io