USB C Type C to Lightning Adapter MFi Certified 4 Pack 27W Fast Charging Support Data Sync,Lightning to USB Type C Cable Adapter for iPhone/iPad/for Airpods,with Anti-Lost Loop,Not for Audio/OTG

So when you connect it to your phone, are you using that USB-C-to-Lightning adapter? If so, then I would say that is your problem. It isn't passing enough power through to fully power on the receiver. The receiver doesn't have a battery; it uses your phone's power. You need an adapter designed to pass power & data; the one in the image is for passing headphone or mic (audio only), which is probably too low powered to run the receiver. Something like https://a.co/d/0cxlcH8V should work.