Why is Pinterest doing weard stuff?

[WPCentral Question]

I recently bought a Nokia Lumia 635 and installed Pinterest. For the first couple of days, everything worked perfectly. But when I tried to open the app today, I got this weird screen, that does give you options to log in and stuff, but not in the format as you would normally get when opening the app.

I hope somebody knows what to do. Thanks in advance.