Plan

Premium

Country

Denmark

Device

iPhone 11 Pro (also on iPhone 8+), Apple Watch 4

Operating System

iOS 13.1.2

Speaker Setup: Heos 1 HS2, Marantz NR1608

So here is what happens:

I try and connect to my speakers using Spotify Connect, but nothing shows up in the menu. However! If - and this took quite a bit of troubleshooting - I turn OFF my watch, they instantly appear along with my PC and my PS4. Very odd. 

What I have tried:

Rebooting all devices

Using my 2.4 GHz network instead of my 5GHz

Unpairing and re-pairing watch (well, I got a new phone so that unpaired it)

Reinstalling Spotify

Deleting Spotify from watch

Signing out and back in

Updating OS/firmware on everything (this issue began for me when I updated my iPhone 8+ to iOS 13.0.0)

Connecting only to one speaker

When I start my watch back up the issue is fixed - until my girlfriend plays something over the speakers using her phone (iPhone XS) and then I'm back to square one.
Oh, and my girlfriend has no problems at all with anything. 

This issue completely stumps me and I hope someone can help!