Failed to send OTP

[sana2024]

hi,
i did everything as the readme says,
i installed the server on aws
run npm install
run node index
and opened port 3000 for it to be reachable through the internet and the server is running fine,

then of front end side i installed the package, changed the host url in otp service, run flutter pub get and run the project on my physical device but after writing my phone number nothing happens and in the log it says failed to send OTP

this is the full error with body

flutter: Exception: Failed to send OTP {"message":"Error","error":"The "key" argument must be of type string or an instance of ArrayBuffer, Buffer, TypedArray, DataView, KeyObject, or CryptoKey. Received undefined"}

[sana2024]

okay i found out i haven't used vonage in my backend, how am i supposed to configure that????