Hi,
As you have not provided any error so I am unable to pinpoint the exact issue. But I am mentioning some of the key reasons due to which customers are unable to login on Magento frontend
1. Missing form_key value:- Insert following code inside <ul class="form-list"> in your login.phtml file.
<input type="hidden" name="form_key" value="<? echo Mage::getSingleton('core/session')->getFormKey(); ?>" />
2.Magento Cache:- Try refreshing magento cache from System -> Cache Management
3.Browser Cache/Cookie:- Clear your browser's cache or cookie and relogin.
<code class="html plain" style="box-sizing: content-box !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; white-space: pre-wrap !important; border-radius: 0px !important; background: none !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !import
