Evernote support got in touch with me (not the robot) and as it turned out, possibly due to a bug, my account remained on the Personal plan even though it should've been downgraded to free, which was then causing the blank billing page.
Finally, support downgraded it to Free and I was able to renew my Personal subscription.
Thank you for all your comments and remarks here and to Evernote support team for solving this!
