That sounds like you have a broken connection to the cable screen. If they have supplied one use the F-type back-to-back (barrel) adapter and use it to connect the aerial direct to the cable feeding the TV socket and see what happens. In the 500 series with purple/blue writing on the aerial the amp is in the VP2 inside box; on older types (with red writing on the aerial) the amp is inside the aerial, a common fault there being loss of the power feed to the amp.
Do some checks and come back with your findings.
I suppose the amp has a working light on it to show it is active?