I had a Twilio account registered with my email address many years ago, now I'm trying to register a SendGrid account, but it says that email is already taken, and it sends me to a Twilio sign in form. I successfully sign in with my Twilio account and it redirects me to SendGrid, where it asks me for my username, but I don't have a SendGrid username, so I try to create one. At this point it realizes I'm already logged in to Twilio, so it says I'm logged in successfully and redirects me to SendGrid where it asks me to input my username. This time I try to input my Twilio email, but the page just redirects to the same place, so I try my username, now it asks me for a password. I try my Twilio password, but it says it's incorrect.

This is what absolute top UX looks like.