Hello André,
Thank you for the information. Yes, unfortunately the latest macOS 10.12 isn’t very good at refreshing the app receipt. This mechanism is crucial for detecting the in-app purchase. Sometimes there is a period of time when the subscription is renewed on the Apple’s server, but macOS doesn’t get this latest state locally. As a result, Telephone doesn’t see it as well.
One of the solutions to make this happen less often is to switch from the monthly to the yearly patronage. You can do this in Apple’s subscription management UI after clicking “Manage Subscriptions...” in Telephone patronage window. Or opening it manually as described here:
https://support.apple.com/en-us/HT202039. The yearly subscription has a small discount.
As an alternative to manually deleting the app you can also press Shift-Command-R when the patronage window is active. You’ll see a dialog to quit the app which will enforce the receipt refresh by the OS.
There’s no way to really fix this and I’ve already filed a bug report at Apple. I’m still looking for a solution to overcome the problem. Sorry for the inconvenience.
Alexey