Only commission earnings can be withdrawn here
Payout create rejected a non-commission source (400 Only commission earnings can be withdrawn here.).
Why this happens
Wrong payout source for this endpoint (e.g. trying to withdraw something other than affiliate commission earnings). Balance transfer and other paths use different rules.
Diagnose and fix
1. Use Request a payout for commission earnings only.
2. For moving commissions to wallet balance, use Transfer affiliate balance to account when enabled.
3. Do not POST arbitrary source values to the payouts API.
4. See Commission payouts are not available for your account if access is blocked entirely.