Update from Appointments+ 1.4 to 1.4.4 not possible

Hi. I just paid 40 dollars, for 1 year update service for the 1.4.4 plugin.
The 1.4.4 versions has an important bug-fix I need for the google calender sync, when clients are deleting a service on the homepage.

When I click the upgrade button, I am redirected to your homepage. When I click the update button here, I am redirected back to my own page.
That is an unlimited looping.

I have tried to download the zip file, and install again. But this is not possible.