It looks like you did not configure SASL on your bucket.
Please verify that the Heroku config vars MEMCACHEDCLOUD_PASSWORD, MEMCACHEDCLOUD_USERNAME have a value in them using the following command:
heroku config -a APP_NAME
If the config vars are empty, please configure SASL authentication for your Memcached Cloud resource using the following steps:
0. [highly recommended] Clear your browser's cache and restart it.
1. SSO in our management console by clicking on the Memcached Cloud add-on in heroku dashboard.
2. Navigate to the Manage Resources page via the top menu (MY RESOURCES->Manage).
3. Click the resource that you wish to edit.
4. Click the Edit button at the Memcached Bucket page's bottom left.
5. Enable SASL Authentication by entering the username and password in the relevant fields under the Access Control & Security section of that page.
6. To apply the changes click the Update button at the page's bottom left.
Your resource will take a couple of seconds to apply the new setting and should have a Pending state. Once it is back to Active you'll need to use your newly-set username and password to access that bucket.