There could be several reasons for not seeing a product available for sale in Odoo:
Multi-Company: If your organization has multiple business entities (companies) set up in Odoo, you might have stock in one company, but you're trying to place an order in another. Make sure you're selecting the right company when creating your sales order.
Multi-Warehouse/Locations: In a single business entity, you might have stock in different warehouse locations. Ensure that you've selected the correct warehouse when creating your sales order.
Reserved Stock: Check the forecast view of the product to see if any stock is reserved for sales or manufacturing orders. This can affect the availability of the product for new orders.
Thanks.