Problem with adding 1S (Color)


I have a problem with adding a new bulb (1S Color) to the Yeelights app. The first bulb is working fine and I had no trouble adding it.
My phone connects to the Bulb and disconnects and repeats this until it says the device is disconnected and that I should try again. I’m choosing the 2.4 ghz WiFi which works on the first bulb. I sat on a chair beneath the bulb while trying to add the device. It seems to find the SSID of the Bulb and when I choose connect it disconnects and reconnects over and over again.

Since the router is provided by the ISP I have unfortunately no option to check the DHCP list.

Troubleshooting steps
1: Reset the bulb two times.
2: Turned off the existing bulb to check if it was a conflict with the first bulb.
3: Cleared Yeelight App cache and rebooted phone.
4: Checked signal strength.

Bulb 1S (Color)
Router provided by ISP Inteno EG300
Phone: OnePlus 6T

Please let me know if you require any further information and what the next troubleshootingstep should be.