The Smappee Genius, Plus, Pro, Energy and Solar all make use of mDNS which in some cases causes issues with the network infrastructure. (DNS servers in particular)
mDNS can be turned off in the expert portal.
More information on how to access this portal can be found here:
How to access the monitor’s expert portal?
The option is found under "Advanced > Advanced checkbox"
Warning: This option is initially needed in order to link the Smappee to the Wifi as the hotspot uses this for IP provisioning, once the monitor is connected to a network it can be turned off.