This is most probably because the app is still being distributed. It takes a couple of hours for the app to the released. This depends on the localisation of the app. if you left this default, the app will be distributed worldwide.
According to Android Authority:
It takes a few hours for the app to appear. The publication process
is automatic and it isn’t too long before your app becomes available
for download.
Wait for a bit and try again. It also seems very wierd from Google, however the label has a grey color, making it seem unavailable. In fact it would be available, when clicking on it.