When you mention that you factory reset the symfonisk speaker, what did you do exactly and what does the LED light currently show? Also what happens when you temporarily cable the speaker to the local network?

When I dit the reset there was an orange light that was blinking. 

At the moment there is a green light blinking. 

Connecting the speaker with a cable does exactly the same as wireless 

Okay, a flashing green light on the speaker is inferring that it’s ready to be added to your existing Sonos Household.

Open a mobile Sonos Controller App (linked to your new routers WiFi network) and ensure you are able to see your ‘other’ setup Sonos products - this must be on a device that (importantly) complies with the mobile requirements mentioned in this link:

https://support.sonos.com/s/article/4875

...and then goto ‘Settings/System/Add Product’ in the App - see if the ‘Add Product’ option then finds the speaker and allows you to set it up in your existing Household.

Settings/System/ will only show my Sonos Move.

When i puch the add product button my phone will keep searching for ours.

It might just be a case that the speaker needs bringing closer to your routers WiFi, or maybe just try power-cycling it first of all (or resetting it again)… see if that helps.

If the problems persist, then you might be best to then contact Sonos Support via this LINK. It could be a case that your new router and it’s settings need some configuration changes, such as disabling QOS or Airtime Fairness etc; but I would have thought in that instance that cabling the one speaker might have worked for you.

So it could be WiFi band isolation perhaps and my thoughts are that it might be quicker to get support staff to assist you, particularly if there are some compatibility issues.