I think what you have is probably working fine. You might be misreading the indicator.
If the indicator is green you should have propane. If the indicator is red then the primary tank needs to be refilled asap. Move the lever or knob to the other tank before you disconnect and fill the empty.
Beware the secondary tank may get low by the time you read the indicator. So it may not seem to last as long as it has been partially used. If running the furnace or other high use check the indicator every morning. If you check in the evening the propane store may close, BTDT.
I have never run out of propane or fiddled with tanks after hours. I fully trust the automatic regulator.