ERROR: Cookies are blocked

I moved a site from domain.com/directory to domain.com today. Had no issues logging in at any point of the site build. Once I moved it I would get a blank white screen at /wp-admin. At /wp-login.php I got the dialog box to login but kept receiving this error: ERROR: Cookies are blocked or not supported by your browser. You must enable cookies to use WordPress.

I searched the forums for a couple hours & tried what was suggested, nothing worked. I then deleted the functions.php from the theme (it is a modified themeforest theme) & tried to login, it worked! However, since the functions.php file was crucial I added it back in. Trying to login again now I am having the same issue all over again. I reached out to the theme developer who got back to me promptly & mentioned they have not heard of that issue with one of their themes yet. They would look into it, but it did not sound promising. Anyone else have any ideas? I have not overwrote or edited any of the theme files. I only edited functions.php based off a forum support topic but after seeing it did not work I removed that code.

Any idea would be helpful as I am not sure of the issue.