Download Auto Cookies MOD
then, unzip it to your computer,
then upload the included install folder, to your phpbb folder on the server.,
then , in your browser, go to:
yourdomain.com/yourphpbbb/install/cookie.php
then click the button to accept the settings it finds.
then delete the install folder.
Then you and all your members MUST do the cookie dance:
step 1. log out
step 2. clear your browser cookie
step 3. clear your browser cache/temporary internet files
step 4. close your browser
step 5. go back and test
done.