Most probably ignoreOlderthan is the culprit here. Splunk may have got restarted and found the file to be older than 5 days and ignored it (put it in the "ignored" list). It'll stay ignored even after new data is being added. Only restart will make it re-evaluated its file monitoring list and data got ingested.
If the data is updated once every 7 days, keep your ignoreOlderthan match that.
What kind of updates does the file get, new data gets appended OR it's completed re-written?