Keval SMS reacted to Struggling with Eververyth in Unable to Log In - "You need to enable cookies before you can use Revive Adserver" - another...
When I clicked on a lnk in an email from my revive ad server installation itself sending my my weekly report I experienced this message for the first time too.
I noticed it sent me to http:// version of the frontend login page of my revive ad server. rather than the https:// version I had been using hence no problems with this You need to enable cookies before you can use error.
I dont know how to fix the cause which would be for the report to redirect you to https:// version
so I just put the s in the url address bar and it went away and I logged in.
Not really a solution but hope it helps someone