Right now bugzilla is turned off as we're migrating to Phabricator. We will update the help text on wikimetrics as soon as we have a new stable environment, sorry for the in-between confusion time.
Now, for your question and the somewhat unfortunate answer
I am trying to run Rolling New Active Editors reports and, having tried on two different computers and with two different cohorts,the report pends for a while and then comes back as failed. Could you possibly have a look into this for me.
This is not your fault or your cohort. Basically, we've been having a lot of troubles with the labs databases which wikimetrics uses to get data. We are currently trying to migrate to a new database where analytics queries are isolated from other kinds of work. That should be much more stable and performant when we get it up. For now, some metrics and some databases (like Rolling New Active Editor and english wikipedia) are mostly crawling and not finishing within the allotted time (1 hour). That's why you see PENDING for so long and then FAILURE. If you see this, you can let us know but unfortunately there's not much we can do until we fix the current database or stand up the new one. Fixing the current database seems to be an effort akin to killing a hydra. Standing up the new one requires lots of coordination with other teams but it's currently our top priority. Sorry again for the inconvenience, I'll look at the db again to see if there's anything simple I can do to help.