Err on display ITC-306T

My 2 year old ITC-306T shows ‘Err’ on the display with a continuous alarm and none of the pushbuttons work. I have restarted it several times with the same result. I have made sure it’s dry and cleaned the metalic probe. My question is - what is the meaning ‘Err’ on the display. If it’s something to do with the probe and would changing the probe be a good idea (perhaps to one on eBay that is fully sealed - suitable for immersion in water etc).

Please understand that the warranty period for the ITC-306T is one year.
The ERR error may be a probe or device failure.
Please check the probe and probe wire for damage.
If they are intact, please contact and my colleague will provide a solution.