Warning: Cannot modify header information – headers already sent by

Hi all,

So I launched a clients website and for whatever reason they seem to be encountering this issue whereby they cannot login.

The issue is baffling as no changes were made but i get this message when trying to login through wp-admin Warning: Cannot modify header information – headers already sent by.

It states the problem is coming from functions.php line 9. I have looked up and down in every file possible and right now I’m at wits end with a severely unhappy client! ??

If i use the functions.php from their old site, it displays fine but the sidebar picks up the old stylesheet coming from where I do not know!!

I have seen previous posts about a similar issue and although helpful, doesn’t seem to have any effect whatsoever.

Can someone PLEASE help me solve this as after 48hrs, i’m no close to solving it.

[please paste large chunks of code at pastebin.com]