NonZeroRefCount

The account cannot be purged because other pallets still reference it. Check the consumers, providers, and sufficients counters in the account's System.Account record; all references must be released first.

Declared by the System pallet; it classifies to the semantic code invalid_argument.

Remediation

Check the argument values against the operation schema

The same explanation is available in the terminal: btcli explain NonZeroRefCount.