If you're holding the stock or it's held elsewhere you will have to call Customer Service to put the sale through. The firm may want you to deliver the stock to the firm before they will let the sale go through.
If the stock is being held by another broker/dealer, once again you will have to call Customer Service to put the order through for you, AND you will need either ACATS forms (which Customer Service can provide you) or have the other broker deliver the stock to E-Trade
However, if the stock is not DTC eligible, you E-Trade may not accept the stock from another broker.
Apparently your account is not long 20,000 shares. If you just bought the stock, make sure payment has been received by E-Trade and you;re not using the proceeds of the sale to pay for the purchase.
Call Customer Service
from the street