WordPress Admin white screen with cookie error

Hello,

I’m having issue’s with my site. Whenever I go to my wp-admin to log in to my wordpress dashboard I get a white screen. I have a client login in my sidebar that uses the wordpress login portal. when i try to log in through that i get an error saying ERROR: Cookies are blocked due to unexpected output. For help, please see this documentation or try the support forums. Can anyone help me with a fix to this? I tried checking the error logs through ftp and i cant open anything in the wp-admin directory. It just fail’s to transfer.