Hi there, thanks for contacting us!
Sam from Moz's Help Team here
When you see a DA of 1, this will usually mean that we haven't indexed that site yet or we haven't found any inbound links for that particular site. That can happen for a number of reasons, such as we haven't found any external links to the site or the site is blocking our crawler or the site is fairly new.
When we compile our index by first crawling the more valuable pages we find and moving on from there. Specific pages may not be crawled if they have lower quality links on them or appear to be part of an unintentional link farm (for example, things like programmed calendars). If you’re wondering why we’re not identifying links to your site, I would suggest checking to make sure we’ve indexed the sites and pages you know are linking to your site.
Also, it’s important to keep in mind that with Link Explorer, new data is added all the time, so please keep an eye out for new data to be available for your site!
Moz's Spam Score is the percentage of sites with similar features we've found to be penalized or banned by Google (it's not based on the spam score of the sites linking to you). To improve this score I would recommend reading our guide which explains the 27 factors used to make up this score. You can then look at your site and investigate areas you would like to improve on your site:
https://moz.com/help/link-explorer/link-building/spam-score
I hope this helps - please let me know if you have any other questions!