Two likely culprits:
1) Is your forwarder sending any data to the indexer? Can you search for index=_internal host=<your forwarder> to determine if nothing is being forwarded?
1a) On your forwarder, also run splunk list forward-server to see if it's probably configured to forward.
2) Your forwarder doesn't have permission to read the logs in question. While logged in to the account the Splunk forwarder is running as, try head /var/log/messages . If you can see the lines, permissions are fine. If not, you need to figure out the linux permissions to allow that account to read the log file.
On another note, I see you have /var/log/messages set to sourcetype cisco:ise:syslog . I can't imagine that file containing data of that sourcetype, at least not primarily. But, this can be worked separately from your forwarding issue.
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