1. supplier problem: the supplier failed to deliver the goods on time, resulting in shortage.
2. Inventory problem: insufficient inventory or inventory can not be adjusted in time, resulting in failure to meet market demand.
3. Changes in market demand: Sudden changes in market demand lead to short supply or oversupply.
4. Policy impact: Policy changes may have an impact on suppliers, manufacturers or sellers, resulting in shortage.
If you need to know more specific reasons, I suggest you contact the supplier or manufacturer of Rongjiang soy sauce for more detailed information.