How do I update my Appointments+ plugin?

Hello. I am not able to update Applintments+, even though I have just extended my membership for this purpose.

After extending my membership, I tried to upgrade directly through the WPMU Dev Dashboard (v. 3.4.2), but all it says is "upgrade to update". When I click on that button, I am taken to this page ( where there is a button, "Install Appointments+". When I click on it, I am given the option to install it on my blog, select it and click "Update to 1.4.1". This action opens a new window with my WPMU Dev's dashboard again, saying "Update to upgrade" - so I am not able to upgrade.

Please help. Thank you.