Trying to pay 59.99€ here, but get a weird message and can’t complete the transaction, even not after restarting the app
For some reason DEVONthink To Go cannot access the App Store. Is your iPhone connected to the internet and DEVONthink To Go is allowed access (via its settings in the Settings app)? Anything else that could keep it from accessing the App Store, firewall, VPN, etc.?
Thanks. We deleted the app and tried again, it is working now, and you have a new customer 
Great, thank you & welcome on board 
Seems this was another case of “something going on inside the App Store black box”.