Same here. App will not sign in (I get an error every time) but I can login to the website. Last night on my phone I wasn't able to login to either the app or the website on my phone. Today, I can login to the website over the phone and computer but still not the app. Even tried deleting and reinstalling the Fly Delta App and that didn't work.

Was worried my account had been locked because yesterday I tried multiple times to change a couple reservations and kept getting errors. Also on a login of the app I got a notice of "This password has appeared in a data leak" with a recommendation to change my password. So I was unsure if through multiple attempts to change flights and changing my password if I had triggered some account security warning that then locked my account but at least with being able to log in to the website this morning, that doesn't seem to the case. Just the app sucking and crashing at the moment.