There Is Condensation In The Stand Steamer's Hose; Too Much Scale Has Built Up In The Stand Steamer - Philips GC558 Troubleshooting Manual

If the water tank is not properly inserted, your garment steamer might not be able to produce
steam.
Please remove the water tank and insert it again correctly.

There is condensation in the stand steamer's hose

When you hold your Philips Garment Steamer horizontally, condensation is created in the hose
and this can block the steam flow. Due to this, your garment steamer could stop steaming or
could start steaming intermittently.
To solve this, lift up your stand steamer's head to straighten the hose vertically and hold your
steamer in an upright position: This will allow any condensation and steam to flow again. After
this, your stand steamer should produce steam again.

Too much scale has built up in the stand steamer

When scale builds up in your Philips Stand Steamer, it might not be able to produce steam.
Please perform the de-calc process detailed in the following lines:
1) Switch off and unplug your stand steamer and allow it to cool down for an hour.
2) Bring the steamer to a sink.
3) Locate the de-calc knob (you will find it on the lower area of the water tank).
4) Turn the de-calc knob anti-clockwise to unlock it.
5) Pull the de-calc knob out and let the water drain.