hmm, trying in this thread.
I can’t seem to be able to add the synch box.
In my hue app on my phone, it shows up in the synch tab as a device (not on my accessory settings page? ) and in homey when selecting the synch box as a device to add, nothing is found.
Same issue for me. I have it installed, but I cannot add it (it just skips the screen and goes to “no devices found”). What can be done to sort it out?
Is your Wifi Connection to the SyncBox working properly ?
Can you reach/connect to your sync box through the “Hue sync” app for your phone/tablet ??
Did you put the syncbox in Discovery mode??
Do you use a Hue bridge ??
Yes on all your questions except the Syncbox is not in discovery mode- doesn’t state that is required?
I’m not 100% sure anymore when or how I added my syncbox about 6 years ago but I remember something like pressing the button on the syncbox until tge led was a specific color to be able to add/pair it with my Homey.
But don’t remember if it was as before or after it was discovered as (new) device. Just wanted to mention that. Is your syncbox on the same (wifi) network??
Is it (a pure) 2.4 GHz wifi network ? Is encapsulation disabled on your wifi network so other wifi devices on the same network can see/connect to eachother??
Install the “Netscan” homey pro app and add a device with the ip adress of your Hue syncbox to ping the network Ip adress of the syncbox. so you can see if your homey can connect/reach the hue syncbox through your Wifi 
network.
Also restart the syncbox by turning off the power for at least 15 seconds and turning the power back on. After that wait about 20 seconds and try again to add the device.
Also try an other Wifi channel to improve the connection.
Yeah. You are refering to when it actually finds it. For some reason me (and the other guys above in the thread) cannot add it because homey cannot find it. It works just fine in the Hue-app etc, no issues there.
And it can ping it on the (Wifi) network (through NetScan app added device with hue syncbox IP-adres ) ??
Do you use only wifi or also the usb lan adapter for your Homey pro ??
Something must be different in the connection specs between the Homey Pro and your phone.
Same Wifi ? Same Wifi frequency 2.4 GHz/5GHz ?
Same local network subnet?
I’m not sure but the Hue syncbox app might connect directly through Bluetooth to the syncbox and not through wifi. Maybe try it by disabling Bluetooth on your phone and the try the Hue syncbox app on your phone. 
Yes, the network is perfectly fine. Perfectly pingable. Same subnet. Same Wifi frequency. All other Hue devices are being discovered from Homey except the Play sync box.
Which version of the Hue bridge are you using?
Do you use any security devices/features like Hue contact sensor or Hue camera’s ?? I’m thinking about a security issue by needing to log in (with your Hue account and not local connection).
Are/were you using matter for the connection/pairing/adding between the homey pro and your hue bridge and/or hue syncbox or the two Philips hue app for Homey Pro from Athom ?? The syncbox itself doesn’t support matter but the hue bridge does for itself and the lights only.
Is this the newest model/version of the syncbox, so 8K or just 4K ? Any revisionnumbers on the box visible ?
