When using Turris Omnia, it attempts to connect to WAN. If you have another router from your provider, to which you have connected the Turris, most probably 192.168.1.1 is used by that router. Hence, no internet will be available to properly go through the wizard.
The workaround is to change the address of the Turris Omnia to e.g. 192.168.2.1 and then all works.
In order for many users to go through the wizard without any problems, please attempt changing the IP address to 192.168.2.1 during the first step of the wizard and use the IP address which was successful in connecting to WAN.
The wizard may notify the user that it has made this change in order for the user to become aware that this was done to avoid a conflict with the current router from their provider.