Basically, there are two possible operating modes:
a) the dimmer can be connected directly to a Hue bulb (but then the connected bulb does not work via the Bridge/App).
b) the dimmer is connected to the bridge (then it is listed in the app as a device and the switching of the bulb also works via the app).
==> it may sound as if mode "a)" is present --> repeat setup according to instructions (beforehand, as already described by Sculp1966, update Bridge and App and check connection for sources of interference, distance etc.). etc.)

Firstly, when was the last time your bridge was updated?
Secondly, is your bridge near a source of interference, next to the router/modem or PC? If so, move the bridge to a different location.
Thirdly, restart the push button with the setup button at the back, hold the push button near a HUE lamp and wait until it is recognised by the system.
it is recognised by the system. Do you also have the new (unfortunately worse) Hue APP?