Option to "add to album" is missing from iphone photos

Hello,

On my iPhone 7 plus, I want to organize my photos into existing photo albums. When I create a new album, I'm able to select photos to add. But for existing albums, when I select photos, click the share icon, the option to "add to album" is missing. It gives me the option to Airdrop, Message, etc., but it no longer shows an option to add to an album. I did the latest ios update and it still doesn't work.

Thoughts?