Their is a section for "SEO moz tool" questions here within the public Q&A.
I was interested to see the wider community's view on why this tool has been down for 7 days and too see if others were also facing issues.
Here is one reply a few days ago:
_I am so sorry that you are running into some issues with our web tools. Rankings, Rank Tracker and our Keyword Difficulty tool all ran into these unexpected outage issues. Unfortunately, Google has changed the way that they present rankings information, so we have had to make some changes to our collection in order to keep up with these changes, I'm afraid that this has caused some issues with providing the real time data for our Rankings and the Keyword Difficulty tool is also currently unresponsive. Our engineers are working tirelessly through this holiday weekend to fix this for you. At this time, unfortunately, we do not have an ETA for when that tool will be up and running again. I thank you for your patience while we work to resolve this issue and I will update you when I have any further information for you. I am hoping for an ETA soon. _
Surprised_ SEOmoz has not posted an official statement about this yet, just a tweet. _
Only thing is we are paying money for tools which are currently having various issues is why an ETA would be good.
It is kind of like paying for a news paper and getting a newspaper with no content in it delivered.