@DMUM 

Consider removing Satellite M9 and M3W from Deco mesh, in Deco app, so that you only have Main Deco M9 left. Then, change it to AP mode.

I remember when I set up my Deco mesh, I started with Main Deco M9, configured it, switched it to AP mode and only then added another Deco.

It worked without any issues for me.

@Alexandre. 

Thanks, this is what I've been trying. Before connecting 2nd and 3rd Mesh "stations", I've been trying to configure the Mesh primary with one of the M9plus, then in APmode, to connect the 2nd and 3rd afterwards.

@TP-Link 

In the deco's bottom it says ver:2.0

TE7M9PLUSV2

this is my network scheme:

I'd like to keep the main router givin the DHCP IPs (some of them are fixed, so I can use home assistant in a easier way)

@DMUM 

In your network diagram I see Main Deco not connected by Ethernet cable to the router. Is this correct, or is this just a typo?

Main Deco must always be connected by Ethernet cable to the router.

@Alexandre. 

Good eyes!!!

I made a mistake in the picture. I already changed it.

Main deco is in the ground floor and connected with wire with router.

secondary deco M9plus, and third deco M3W should be connected to the main one wirelessly.

the problem is that main one once I set it up as "wireless router" creates its on address block and work. But I set it up as AP, it restarts, yellow light, and allways turns red. 

@DMUM 

The only thing I would recommend is start fresh. Remove all Decos from your home network in Deco app, and after you did that also reset them manually as described in this document: How can I reset or reboot my Deco Whole-Home Wi-Fi System?

Keep all three Deco units powered off.

Then, take your M9Plus which was not Main Deco, bring it to your wireless router and connect directly to one of router ports with short Ethernet cable. Add that M9Plus to your Deco mesh as if you start anew, and it'll become Main Deco. After initial setup complete, when you see that Deco LED is green and stays green (wait few minutes to ensure), in Deco app try again to change Deco mesh Operating Mode to Access Point.

Make sure you give Main Deco 5 to 10 minutes to reconfigure itself. Its LED could go green, red, green again. If it ended with steady green after 5-10 minutes, it is success.

This is the simplest possible configuration and it should work. If it does not, you'll need @TP-Link help at this point.

Also, TP-Link asked you for brand name and model number of your wireless router. If that simple setup I suggested does not work, please provide that information in your response.