The code should work fine as suggested by Pankaj however, I cannot see the external file custom.css stylesheet reference being called in your template due to directory path not seen right while viewing page source. The css attribute can also be seen here as added by you
Kindly check screenshot where I had added specific css attribute and it works fine in responsive mode
Try add this external stylesheet reference in the field - Before </head> as seen in screenshot in template >> custom code
<link href=”https://www.macaucentral.com/templates/ja_megastore/css/custom.css” rel=”stylesheet”>
also see the remember me checkbox
Try change this in custom.css file:
@media(max-width:768px){#hikashop_checkout_login_form .input-prepend {display: flex;}}
to
@media(max-width:768px){#hikashop_checkout_login_form .input-prepend, #hikashop_checkout_login_form #form-login-remember {display: flex;}
#hikashop_checkout_login_form .checkbox input[type="checkbox"]{margin-left:-10px !important;}
}
and adjust margin value accordingly
Do ensure to clear your browser cache if changes dont reflect