A320 - Is VS Function not Functioning?

Flying the A320 out of Darwin to Taipei.
Desired ALT set at 30,000’.
The VS setting initially worked but at 5,000’ the climb levelled off & despite trying various measures I was unable to get the aircraft back on a climb.
Is the VS currently faulty?

Is the FMA showing ALT in magenta colour? If so, you might be approaching a waypoint with an altitude constraint. If the waypoint you’re heading has a 5,000 ft altitude constraint on departure, it will level off at 5,000 until it passed that waypoint. Then the aircraft will continue the climb.

Personally, I never liked using V/S Mode. I just use managed climb mode. Set the desired altitude, push the altitude knob and let it climb on its own all the way to the cruising altitude.

If you want to override those constraints, you need to pull the altitude knob to engage Selected or Open climb mode, then you can either let it climb using the calculated optimal climb profile automatically, or override using the V/S.

Could be it.
I’ll try the Managed Climb on ALT.

Can confirm your ALT method works. I’ll ignore VS from now on.