I have loki setup in docker and it shows no logs. I can confirm that the logs are coming to Loki as I tried the following steps:
Started loki and grafana and logged in to check the logs. There are no logs and then Log browser doesnt show any labels.
Then I started my application and after it has pushed some logs, I can see the label and their possible values in the log browser to construct the query but it still shows no logs.
My problem turned out to be that the log source was applying the time zone offset but not showing it in the time format. As a result, the time zone offset was being subtracted twice. If I looked back 6 hours I would see my current data. To fix it, I set the time zone of my reporting devices (fortunately I only have 2) to UTC.