Bad!!!
Response from developer
Hello, We are actually having issues with OTP verification. We are using Firebase API for OTP verification. Firebase recently suddenly changed their policy of OTP verification on development side without any nofication for us. We are working hard to fix the issue and will submit update in 3-4 days. iTunes manages all the payments. Could you please follow the instructions to request refund? https://support.apple.com/en-us/HT204084