Polymorfa does not store real WhatsApp message history by default. History access requires explicitly enabled storage and the eligible history feature for that number and project. Testing numbers do not provide real hosted history.
Check whether storage was enabled when the messages occurred, along with your current access. A blank view is not proof that those messages were retained. Tell support the time range, number reference, and displayed result. Do not assume that enabling storage now will recover earlier conversations or that support can retrieve messages never stored.