Why are clients being asked to sign into client portal?

When I sent an invoice the client clicked pay now and was directed to a login screen. This hasn’t happened before now. When I check the link from client portal in a incognito tab it also prompts me to sign in. How can I get back to configuration where clients do not need to login?

In Settings > Client Portal > Authorization

disable Password Protection.

This is already disabled

actually, I guess it wasn’t disabled in the group settings. So odd, I have many clients in this group and they’ve never had an issue with this. Thanks