Same issue here. I have a Sengled light strips and can’t get SmartThings to recognize it. I try to add the Device by Brand. Under the Sengland lighting option you can add Sengled, Singled Smart LED ZigBee and you can find a Sengled Wifi bulb and pick the exact product - I’ve tried each option and it fails every single time.
I’ll add in that the lights have been found by the Sengled App and Alexa. I’ve also reset the lights, my SmartThings Hub and rebooted my router all a few times.
Hoping someone out there has the magical answer.