Login form invisible

Until recently my UM was working perfectly, but this week I had a report that the Login page wasn’t working. I checked it out and there’s a big blank space where the username / password login box is normally.

I suspect it’s there but just not visible, as if I hover over it I get suggested username and password from my password manager. So could it be a theme issue (OceanWP theme, in my case)?

I tried deleting and recreating the login form but it didn’t help. If I log in as an admin with my wodpress.com login I can see the other forms (Your Account, Profile, Logout) OK. But as a logged-out user the Login form isn’t visible.

Any ideas welcome!?

The page I need help with: [log in to see the link]