Yes same issue too. Nothing work. Reinstalling members app doesn't do the trick. Neither clearing cache or data. I successfully register the day it got announced, but still haven't able to download the beta.
I dont even have the pop up to enroll, despite having a factory unlocked phone. Its limited to like 15,000 participants every beta I think. I guess a lot of people are also signing up for this beta, a lot more than we might think.