I opened my second shop a while ago.
When I did, I signed out, clicked "Sell on Etsy" and they asked me for a different email address. I had to use three different ones... one for each of my shops.
Now, I think you can sign in with Facebook and/or Google. If you have both, try signing in with the other. Maybe this will work for you.
(Since no one replied, I thought I would add a suggestion. I hope it helps.)
If not, I would "contact Etsy". Good Luck to all of you!
JulsSewCrazy.etsy.com
JulsCraftCrazy.etsy.com
HalfToHaveIt.etsy.com
(Each shop has a different email.)