WP Admin login won't come up

The WP Admin login start page no longer comes up for my website. I get the following warning message:

Warning: Cannot modify header information – headers already sent by (output started at /home/rtoker/betternxt.com/wp-content/themes/inovado/functions.php:1) in /home/rtoker/betternxt.com/wp-includes/pluggable.php on line 876

Does anyone know what fix I should make to resolve this issue?

Thanks