My Dyson TP00 is connected to the WiFi (symbol on the device) and can be found in the app. When I try to connect it within the app the connection always fails for unknown reasons. In the second step the app shows “slow reaction” and it never connects to the the device. 

I tried dual band (2.4 and 5 GHz) and as recommended the single one (only 2.4 GHz), nothing helps.