Cookies are blocked due to unexpected output.

I am maintaining a site an have recently been blocked from logging in due to the following error:

ERROR: Cookies are blocked due to unexpected output. For help, please see this documentation or try the support forums.

I used Filezilla to rename all of the plugins to see if I could narrow it down to an issue with one of them but to no avail. Looking through the forums I did reference a few posts about this error but I was unable to derive a likely solution after trying a couple.

Note: I do have the Wordfence plugin installed and am getting an email verification that my login authenticates.

This seemed to occur after the 4.2.2 update however I’m not sure. Thanks in advance for your input.