Collaborator listed as "non-collaborator" in automation

I’m trying to have emails automatically sent to someone in another organization but who is shared as a “Creator” on the workplace on a free plan but it’s saying that they are not a collaborator and can’t have notifications sent. The addresses are the same, and it’s (I believe) the account that manages their account so why is this not working?

Looks like you’re including an email address but also a field called “Due Date” which doesn’t sound like its in the form of an email.

Take the last part out, does it work with just the typed in email address?

No, it didn’t work without that either! And when I tried to put a space between the two it said the email wasn’t valid anymore. This is the error I’m getting: