I have experienced with Android 10 that the passcode reset works not 100% stable (as many other things too in WS1). Sometime it works, sometimes not.
I tried the reset on two equal test devices at almost the same moment. On one device the passcode was reset in seconds. On the other device i needs a few hours. So maybe you just repeat and wait? I'm not sure if synchronizing the device has an effect.
Maybe instead of use 'Clear Passcode > Device', you could try 'Management > Change Device Passcode'.