PDF not fillable

I have a PDF that says it's fillable, but when I open it in Acrobat and Reader, I can't enter any information into the form fields. As soon as I try, it asks for a password. I don’t have the password, and I’m not trying to bypass or recover it.  

When I check the file’s security settings, it shows that

filling of form fields

printing

document assembly

signing

template pages are all allowed.

So I’m not sure why it’s behaving this way.  Am I missing something? Or is this possibly a damaged or misconfigured file? Just trying to figure out whether I need to go back and ask for a different version.

Thanks in advance.
Tim