I realise I may be teaching granny to suck eggs but if there is an amplifier make sure it is turned on.
Our first van had an omni directional aerial and we never used it because we could not get anything on it,we used a household one instead.
When I was emptying the van for PX I found an amplifier in a very difficult position to spot and it had of course been turned off to save the batteries, I was never aware it had an amp.
We find our existing Status 530 unidirectional aerial and amp very good.