Flashing warning triangle on AEG freezer

[Tony Collier]

I have an AEG Arctis Freezer model A72710GNX0. The temperature warning triangle is continuously flashing. When I press either the + or - buttons the display does not change. From reading the manual I understand that the actual temp is displayed for a few seconds and then reverts to the desired temp. I assume as this is not happening both the actual and desired temps are the same so all ok. I have tried turning off but no difference apart from the audible alarm sounds for an hour
Is there a way to reset the flashing triangle as it seems to be 'stuck' on. TIA