SmartThings hub cannot find hue hub

I’m currently used an old, custom Hue DTH which is obviously becoming redundant very soon. so I’m trying to integrate my hub with Hue. Both ST hub and Hue hub are on the latest firmware, both on the same network and both etherneted into the same switch even.
I select “Philips Hue with SmartThings Hub” then select my ST hub and room.
It then tells me to unplug the ethernet cable of the hue bridge, wait 10 seconds, plug it in and press the button, etc.
I’ve tried so many variations of this, including rebooting both hubs, but whatever I try after a while it times out saying “There was a problem connecting to the device. Try again. Error code: 34-302”
Any ideas of what I can try next?

reboot both your ST hub and router

also make sure you removed the custom smartapp and device handlers in IDE

Yes, also rebooted my router.
I probably should remove the custom smartapp and device handlers, I’m a little concerned about doing so as it will mean no light control if it doesn’t work.