My A90 (15 months old) had no signs of life today when I tried to turn it on. I couldn't hear the usual click of the relay when I turned it on.
In case it's useful for anyone else, the fuse (inside the holder next to the power input on the back of the A90) had blown. I swapped the blown fuse for the supplied spare which was inside the holder and my A90 worked fine again. I ordered a spare pack of fuses (only £2.10 from Amazon UK) - "10 x 500mA 0.5A 20mm Glass Quick Fast Blow Fuse (Pack of 10)" - https://www.amazon.co.uk/500mA-20mm-Glass-Quick-Blow/dp/B013ECCE6I
In case it's useful for anyone else, the fuse (inside the holder next to the power input on the back of the A90) had blown. I swapped the blown fuse for the supplied spare which was inside the holder and my A90 worked fine again. I ordered a spare pack of fuses (only £2.10 from Amazon UK) - "10 x 500mA 0.5A 20mm Glass Quick Fast Blow Fuse (Pack of 10)" - https://www.amazon.co.uk/500mA-20mm-Glass-Quick-Blow/dp/B013ECCE6I