There are two points you should check. The log file is perfectly normal if the inventory script was running in the last 4 hours. This script creates a timestamp file and checks at start if it is older than the configured time. If not it will exit immediately.
That means - remove the timestamp and inspect the log file after the next agent run.
The other point you can check is the stored persisted data for this host on the monitoring system.
Inside “~/var/check_mk/persisted/” you should find a file with the data from this host and inside is hopefully some useful data.