Aux cable- iPhone 8

Hi. I purchased a Baseus Lightning to Aux adaptor to play music off of my iPhone 8. The Phone detects it and selects it as a ‘Dock’ speaker when I connect the aux cable to it but nothing is transmitted. I tried 2 different adaptors on 2 different phones and it didn’t work except for once when I followed another troubleshooting guide which told me to switch Bluetooth off on the phone. Subsequent attempts, however, didn’t work. When I plug headphones into the adaptor, it works.

Any idea what the issue might be? The fact that it worked just the once makes me think that there’s some setting that might affect its behavior.