Cannot renew subscription

I sent an email regarding an issue renewing my subscription. You sent out instructions for ordering with a PO.  When I click on the link to upgrade this is what I get: 

Unable to switch subscription. Please use BlueSnap(Plimus) control panel to change your subscription manually.

When I click on the link it comes up with an error.  I just need an invoice to renew my subscription.  If I can't do it through your website and you cant send me one then there is no way to renew before my subscription ends.

You seem to be upgrading to a higher plan and not a silver plan or the same subscription? Can you please confirm? Click the upgrade button for the same plan will work. Please give it a try and let us know how it goes.