This is referred to as having a boxed position in which the account is technically either flat in the symbol or is really only holding 1 side of the position. It happens at almost all clearing brokers and can occur during the settlement process of the trades if the account switches from cash to margin or margin to cash. In most cases, it gets cleared up on its own once settlement is completed. However, as this may impact the account buying power, it is recommended that you contact your clearing broker and have them flatten out the position on their end. If you don’t get it resolved by the broker, the issue will remain that way daily until it is settled.