The charge rate will drop if you have long or poor quality extension leads.
If you can find one with 1.5mm conductors (Like on on 15A extension leads) that may help. (NOTE: 15A Plugs and sockets are different)
I am charging with granny charger for the first time and it says 1.4kw charging power
Is it ok? Depends on your needs. Is it normal? Yes, new deliveries get an 8A EVSE, where previous ones got a 10A EVSE. 8A is about 1.8 kW, but the atto3 seems to both draw less than the supply rating and measure charge rate after losses, bringing it down to about 1.4 kW.