Don't know if this will help, but I think if you had enough at the end of Feb you will probably get your check in April. I believe they mail checks at the end of the month following when you met the $20 cashout.
Also, make sure you check under the "My Account" link. I know a lot of people don't get their checks when they are suppose to because they have not "verified" their account. When you look under "My Account" link (from Netflip help):
To verify your email address please go to "My Account" and login. If you have not already verified your email address, there will be a red link at the bottom of the page requesting you to do so. Click on the link. A pop up window will appear telling you that a message has been sent to your email address. Go to your email account and open up the message. Inside the message there will be a link that will verify your email address. Click on the link and a browser will open letting you know that you are verified. If you cannot click on the link, cut and paste it into your browser.
Good luck.