@phad 

You may be able to fix that by logging to Main Deco Web interface.

Open Main Deco IP address in browser on device connected to Deco mesh. If you run Deco mesh in Router mode with no changes to default LAN settings that IP address should be 192.168.68.1

The login page should appear. There is no user name to enter, just password. Enter same password you use to login to Deco app.

If login was successful, open Advanced/System/Time Settings and select correct region and city, example:

Make sure you save your selection, Save button should appear in bottom right corner of that page.

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More detailed version of that can be found in TP-Link FAQ: How to log into the web-based interface of my Deco

  @Alexandre. 

Hello,

Thank you for replying. Unfortunately this was already set to Europe/Stockholm when I logged in.

  @phad 

OK, let's try some other things. Your Main Deco, is it connected to ISP gateway/router or to ISP modem? 

  @Alexandre. 

It's connected directly into the modem

phad wrote

  @Alexandre. 

 

It's connected directly into the modem

  @phad 

But it is modem, not router, right? Can you give me its brand name and model number, just to be sure? Some ISPs mistakenly name their box "modem" while in fact it is router.

The most common ways for Internet Web site to figure your location is from your household WAN IP address and from DNS servers that are used by your ISP router or Main Deco. 

If you have ISP router, it would be possible to set Deco to piggyback on its settings, and you are saying these settings are correct - when you connect laptop "directly to the box."

  @Alexandre. 

It has no brand or info on it. But it is the box that the fiber goes to, so it's no router.

  @phad 

Thanks for the photo, very helpful.

This box has four Ethernet ports. One is up, that must be one to which Main Deco is connected.

Please do the test: connect laptop to one of remaining three Ethernet ports (LAN2-LAN4), do not disconnect Main Deco from LAN1 port. If laptop can connect to Internet and its port LED goes green, while LAN1 LED stays green, this box is configured as a router and I may have simple solution for you.

  @Alexandre. 

Oh okey. Yes I could connect a laptop to a second port and they both stay green

  @phad 

Great. Then, what you have is router and it is configured as router. If it were modem or router configured in modem mode, only one LAN port could be active.

Because it is in fact router, you can configure Deco mesh to run in Access Point mode. In that mode, Deco mesh will piggyback on all "box" networking settings. The problem with wrong geolocation should go away, I am 99% confident.

For steps, see Switching a Deco to Access Point (AP) Mode

  @Alexandre. 

Did the steps and now the units just stays red...tried to cut the power and start again, no luck