503 Error or 200 OK??

[wiredseo]

So, in a Moz crawl and a Screaming From crawl, I'm getting some 503 Service Unavailable responses on the some pages.

So I go to the pages in question, and the Moz bar is showing a 200 OK.  The SEOBook http status checker (http://tools.seobook.com/server-header-checker/) also shows a 200 OK.

What gives?

The only reason I'm looking at this is because rankings plummeted a couple of weeks ago.

Thanks!

UPDATE

So, I decided to use the mozbar to set the user agent as Googlebot and when I tried to access the pages in question I receive this message.  I don't think this is an issue... anyone else have much experience here?

Your access to this site has been limited

Your access to this service has been temporarily limited. Please try again in a few minutes. (HTTP response code 503)

Reason: Fake Google crawler automatically blocked

Important note for site admins: If you are the administrator of this website note that your access has been limited because you broke one of the Wordfence firewall rules. The reason you access was limited is: "Fake Google crawler automatically blocked".

If this is a false positive, meaning that your access to your own site has been limited incorrectly, then you will need to regain access to your site, go to the Wordfence "options" page, go to the section for Firewall Rules and disable the rule that caused you to be blocked. For example, if you were blocked because it was detected that you are a fake Google crawler, then disable the rule that blocks fake google crawlers. Or if you were blocked because you were accessing your site too quickly, then increase the number of accesses allowed per minute.

If you're still having trouble, then simply disable the Wordfence firewall and you will still benefit from the other security features that Wordfence provides.

If you are a site administrator and have been accidentally locked out, please enter your email in the box below and click "Send". If the email address you enter belongs to a known site administrator or someone set to receive Wordfence alerts, we will send you an email to help you regain access. Please read our FAQ if this does not work.

[FedeEinhorn]

The problem is that plugin you are using, "Wordfence". It is probably picking up the crawls from Screaming Frog and Moz as DoS attacks because of the amount of requests from the same IPs.

You could either see if the plugin IP whitelisting or why don't you just remove that plugin and use CloudFlare, which is free and offer an even more robust security option + an included CDN.