I can see the logs on the indexer but they aren't searchable on search head.
I've already checked for -
This indexer is also the license master.
Hi,
Follow the procedure in documents for adding search peer:
https://docs.splunk.com/Documentation/Splunk/7.0.2/DistSearch/Configuredistributedsearch
Have you added your idx as search peers?
You can try
|tstats count where index=* by index