I have found that in order to use the website builder on Chrome - you have to disable ALL extensions and turn off blocking of 3rd party cookies. Constant Contact has several multiple cookies (holy cow!)
Instead, I opted for Firefox browser. Only using this builder for a client who is using it. If it were up to me, I'd steer anyone who wants a professional website (not some kindergarten version) to use a developer/designer.
Thank you for sharing your workaround here in the Community! I apologize if you too have had this same experience with logging into our Website Builder. We are however happy to hear you were able to determine a workaround that works for you. Please let us know if there is anything else we can assist with in the meantime.