Using a WIFI 3-way switch to replace one of two switches

[hitechseeker]

I had a 3-way setup using two mechanical switches, and everything was working fine.
However I decided to add "intelligence" to the system by replacing one of the switches with a WIFI switch.
The WIFI switch works fine and can be controlled with Google, however the setup does not work well.
The one Mechanical switch can only be used to turn on or off IF the WIFI switch is actively on.
Switch manufacturer shows that a Mechanical and one WIFI switch ( made by Tessan) should work fine.
Its a minor inconvenience and I would really to understand the reason for this even if the issue cannot be fixed.
How do I diagnose ?

 

[AC Power]

I am assuming you've connected the "travelers" correctly?

 

[hitechseeker]

Thanks for the reply.
The switch "sort of works", but has a different behavior than an arrangement with two mechanical switches.
The single mechanical switch has to be pushed off and on to activate.
I am going to replace the mechanical switch with another Tessan switch, so both are SMART switches, and see if that arrangement works any better.
The one mechanical and one SMART switch works fine with Google, but sometimes I just want to push the button for mechanical switching without involving Google.

 

[AC Power]

I see.....well,

All The Best with that!