Make sure you are using the right index as your data may be in 'x-index' as splunk default index is 'main' so include your search with respective index and sourcetype too in .And you must have access to those indexes..
Make sure your Indexer or search peers are active(Seach head able to fetch data from it)
Check in inputs.conf too..
If possible check the timestamp in logs and search for that specific time range instead of all time.
Sorry for the confusion, let me clarify. If your access level only allows a search for 30 days, you won't be able to see the "All Time" results. The "All Time" results would fall out of the range for the 30 day period.