Did Penguin affect my site or conversions? (attached screenshot)

Hi all,

Our site is a software site and our goal = signups. We've been getting very few organic signups lately (as compared to July or August) so I looked into the Possum update and unofficial Penguin update in September again.

Our business isn't local, it's cloud-based/global so possum shouldn't have affected us. Previously I made a post about how our best keywords' organic impressions dropped a lot, many members responded and told me that it's due to the Penguin update. However when I looked into WebmasterTools -> Links to your site, none was spammy/fake.

What I've noticed was that when the Penguin was first rolled out, our brand name keyword was pushed from 1st page 5th position to page 5... and 1st page was filled with low relevance, poorly made sites. Since a week ago our site's back to its original position which is good, but the real issue remains, which is that we're still getting really low organic signups.

Comparing Ranking/Position vs Conversions from Aug 15 - Oct 15:



As you can see above (Aug 15 - Oct 15), our ranking took a big hit on Sept 22 (which is 1 day before when Penguin's allegedly released), and was back up and stabilized after Oct 6.



Whereas for conversions, it seems have dropped on Sept 15 and never really came back up.

Comparing Sept 15-Oct 15 vs. Aug 15-Sept 14, our impressions dropped 25%, but conversions dropped a whopping 63%

I also had a few 404s here and there in the last 2 months, but I check Crawl Errors everyday and fixed them as soon as it's reported. Would that have affected my ranking?

Anyway, I really want to know why our signups dropped so much and how we could get the numbers back up... Part of it might be due to the seasonality but definitely not all. Any insight is greatly appreciated!!!