Spotify Connect devices not appearing unless I login to desktop client

[gotoid]

Plan

Premium

Device

OnePlus 3, OnePlus 5

Operating System

Android Oreo, MacOS 10.13

My Question or Issue

I have the Spotify app installed on a first gen Amazon FireTV. I can connect to it via Spotify Connect, and play music just fine.

The problem presents itself when someone else connects to the FireTV via their device (tested with, 2 x Nexus 5X, OnePlus 5, iPhone 5SE, all with Spotify premium accounts).

They can connect and play music, but when I try to connect back, my devices (OnePlus 3, OnePlus 5) dont display the FireTV on the devices list. The only way I have managed to get the phones to display the FireTV is to run the Spotify desktop client on my mac. After that, my devices will also display the FireTV.

The same problem can be observed on the KEF LS50 Wireless speakers. The only device which is displayed on all devices no matter what, is my Chromecast.

As you can imagine this is a cumbersome solution to this issue I am experiencing. Please help. If I you need any additional information please let me know.

CORRECTION

I need need to run the desktop client and CONNECT to the device (FireTV or LS50 speakers) for my Oneplus 3 / 5 to display the device on my list.