While running this setup:

Where Router1 is connected to Router2 via LAN to LAN port, I try to initialize OneMesh network, but getting "Operation Failed" error.

This is the route to the error:

• from web interface http://192.168.1.1 of Router 1
• I enter Advanced settings
• and select OneMesh option
• where I see correctly, my Router 2 (that sits on http://192.168.1.2)
• and by pressing OK button the "Operation Failed" error appears on bottom and nothing happens

Alternatives:

• I also tried to re-plug the cable into WAN port like Router_1_LAN >>> WAN_Router_2 but with this kind of setup none of the both routers detect the other one and I get only this dumb screen: 

Questions:

• how can be this error resolved?
• what kind of settings needs to be triggered to initialize OneMesh between two routers?
• what did I miss to set up? (as non-IT person I have no idea what I'm doing)