The hydraulics need a lot of stored power from the battery to get the hydraulic pump going. Less power is needed for the electric slides. So it's possible that you're getting enough power through the shore power connection to run the slides, but not enough to run the hydraulics, if your battery is low.
Another possibility is a problem at the dual polarity solenoid that connects power and ground to the hydraulic pump. If you have a loose connection there, it might account for the clicking sound.
To test your battery, turn off or disconnect shore power. Wait about 10 minutes. Then go to the levelup control panel and cycle it to see the voltage reading. If you have 12.5 - 12.6V, your battery is fully charged. If 12.0 or less, it's pretty much discharged. But shore power has to be disconnected or the reading will reflect the output of the Power Converter instead of the battery.
If the battery has a good charge of 12.5 - 12.6, check at the hydraulic pump to see if the thick wires are tightly connected.
Another possibility is a poor ground connection from the dual polarity solenoid to the frame. Here's a diagram that might help.