Magento frontend customer login doesn’t work and loops back to login with no message 35$

We recently hired a freelancer to make minor changes to Magento (place Login button and cart in the upper right side of the page). Didn't do such a great job and now quite a few of our store users on [login to view URL] are reporting this issue on multiple browsers except Safari. They try and login and cannot, they are simply looped back to the login page with no explanation whatsoever, no number of tries makes it work, making the store unusable for them. We've tested it ourselves and indeed it doesn't work in Chrome, Firefox, Explorer. These are the login pages: [login to view URL] OR [login to view URL] once you've placed a product in the cart and click on the CLIENT INREGISTRAT (registered client) tab. An example of a user is: biancatheodoru(at)[login to view URL] password: bianca Only people that are experienced in Magento please.