This is a note for myself (as much) as for anyone else.
I run EyeTV 3.6.9 on an old Mac Mini 2007 (OSX 10.6.8) - "Snow Leopard" using a HomeRUN network tuner.
Its been a sweet spot of stability for years.. upgrading either EyeTV or OSX introduced instabilities.. it runs reliably without updating.
TVGuide EPG renewals (go smoothly) if you pay online through Paypal, a few minutes later an email arrives (at the original email address for the EyeTV subscription signed up with Geniatech)(not necessarily the same as your Paypal email address). Included in the email is a "Link to activate:"
That "Link" includes the Subscription key embedded within the link.
I manually open a window on OSX, and use the original Apple Safari browser and manually type the "Link to activate:" with the Subscription key embedded into the Safari address bar then press "Enter"
Safari does not browse to the website link, instead it activates the EyeTV program, which then "automatically" performs the renewal and activation while you watch.
I regularly use other browsers and other operating systems on other computers. (None) of those browsers, operating systems or computers will start the EyeTV program on my original Mac Mini 2007 (OSX 10.6.8) and automatically perform the renewal and activation. You have to perform the renewal and activation on the computer where EyeTV is run, using the Safari browser on that computer.
I have never asked technical support for help, but it is possible they have a "Way" to do this for you from their side, which while convenient, may not be the best solution if you wish to understand and do it yourself.
Have a nice day.