Thanks for the answer, Actually checking mongod.log file we found out that the key used with the certificate bound to port 8089 could not be read . Therfore the service was not started. So we removed that key and now it is ok.
The problem is that in our environment we need to change the default certs of splunk and use ours. So we have to check how can we use our certs in order not to cause issue to the system