For some reason my clients can only login to the client portal form Firefox, not Safari or Chrome !! i have the iframe setup on my website. they can login using the direct client link but not from the iframe.
It may be from the iFrame, I suggest trying to disable the feature.
I’m using an iframe code generated using the Client Login direct link <iframe src="https://mydomain.com/invoicing/public/client/login?account_key=9afr8scp3jelarvsz6nyuirgwfxrzobb" style="border:0px #ffffff none;" name="myiFrame" scrolling="yes" frameborder="0" marginheight="0px" marginwidth="0px" height="1550px" width="1200px" allowfullscreen></iframe>
I believe that may be related to the problem, I suggest trying to remove it