AWS IoT unable to invoke lambda function

Hi all,

I am new to AWS, and was trying to setup an IoT system where a lambda function is triggered whenever messages are received. Whenever I receive the message, however, the lambda function is not invoked (although I know the message has been received and parsed correctly). Looking at the logs, I see the message iot.amazonaws.com is unable to perform: lambda:InvokeFunction on resource: arn:aws:lambda:eu-west-3:216554370311:function:[...]. I have added permissions to AWS IoT as referenced here, and I am currently at a loss on what could be the cause of such behavior.

Has any of you faced this error?

Thanks