Thank you for the added Information.
You have some problems with your certificates. Not sure where/how you made them but double check that you have the right ones in the keystore. Also make sure Graylog has access to the keystore and the certificates.
Question: are you trying to use HTTPS or just certificates for your INPUT?
Have you seen these as shown below? I used both sites at one point which help me learn how to fix my issues maybe they will help also.
EDIT:
What happens when you comment this out?
http_publish_uri = https://hostname/