I mailed my mn state return on March 6th and am yet to see my refund. I continue checking the "where's my refund" site and the status is checking for accuracy. 3 months?

So the MN Dept. of Revenue website was at least able to find evidence of your return at this link?

https://www.mndor.state.mn.us/tp/refund

You can phone the MN Dept. of Revenue to see if you can learn anything about the delay.

To get the phone number, at the link below scroll down to where it says "For Individual Taxpayers--Individual Income Tax."  There is both a local and an 800 number.
http://www.revenue.state.mn.us/Pages/contact_us_page.aspx

If you can't get good info from the D.O.R, then on that same contact page, scroll WAY down to near the bottom, and  you will see the phone number for the "Taxpayer Rights Advocate."  That office may be able to assist you in finding out more about the delay or tweaking things.

I also found a website for the Taxpayer Rights Advocate, which has the phone number if you end up needing to contact them.
<a rel="nofollow" target="_blank" href="http://www.revenue.state.mn.us/taxpayer_rights/Pages/Taxpayer_Rights.aspx">http://www.revenue.state.mn.us/taxpayer_rights/Pages/Taxpayer_Rights.aspx</a>