What you need to check is whether you have selected the correct server in the pull down menu of the newsgroups.
If you choose for ‘New subscription’ at the bottom of the subscriptions panel a window will open with newsgroups. In the top left of this window is a pulldown menu. Make sure you have selected the correct server here.
If this is all correct then something strange is going on and you will probably have to go back to the factory settings.
The steps for this can be found in:
https://www.usenapp.com/forum/d/324-reset-usenapp-to-default-settings
You received the activation key by email after your purchase.
You can also find the key at:
https://www.xoroxsoft.com/account/licenses/