URL can not be found by Play Store after purchase

[Tented]

I have been an user of Poweramp music player for a long time, thouroughly enjoying the equalizer. So when I learned that there would be a standalone equalizer I was over the moon. I tried to upgrade to premium since last saturday (so far trying 4 times, every time it fails) but I keep getting the "Unable to find URL" (Translated from Dutch to English) screen as provided in the attachments. My purchases are restored automatically after getting this link, I did not press restore purchases (tried to purchase again this morning). I updated every Google service on my phone and made sure I am logged in on everything I can be logged in with. I looked through the other posts about this topic and tried everything but also to no avail. Could anyone help me or point me in the right direction?