All input notes are half a note higher than the actual notes heard
this sort of thing is most commonly caused by your audio device sample rate not matching what it says in Dorico (in Preferences–> Play–> Audio setup) – often because it has been changed by another audio application. A different sample rate causes pitches to vary.
That’s right what dko22 says. Therefore, go to Edit > Device Setup and reassert the wanted sample rate, i.e. click again on the wanted sample rate in the drop down menu, then everything shall be fine again.