I have a private VPC with a VPC endpoint to Secrets Manager and a rotation function. Secrets manager is able to invoke the function, but the function can only intermittently communicate with secrets manager. I can see it calls the Secrets Manager API a number of times successfully, but after calling GetRandomPassword it just says "Resetting dropped connection".
For full details see the following post:
https://stackoverflow.com/questions/71807653/secrets-manager-rotation-timeout