Works with S20 but not S10

Hi. I got a Razer Kishi controller for my son's Samsung Galaxy S10. We connected it but the controller doesn't respond (no blue light). I tried it on my S20 and it comes on straight away, so the controller works. I have looked at the accessibility options on the S10 and switched everything off but that doesn't work either. I wondered if it could be a connection problem but I have cleaned the charging port and the phone charges just fine. Can anyone suggest anything else we could try?