Calibration of pH Machine

[beanPoolOwner]

I have a pH machine PoolBasic Evo+ that is used to automatically add pH solution to the pool.

The pH reading is stuck at 5 pH, even though my pool is at 7pH.

I thought maybe I needed to calibrate the machine, so I bought some 7pH solution and put the probe in it:

Unfortunately, after the 1 minute to calibrate, I get this error :

Anyone knows what the problem might be?

Thanks!