Hi Aung
from your problem you can follow this
1. Right-click on the layer that is not displaying, then choose “Repair Data Source” to point it to the correct file location.
2. Go to Project > Properties > General, and check or adjust the “Save paths” setting. If your files have been moved, make sure it’s set to “Relative” only if the folder structure is the same. Otherwise, switch to “Absolute” paths to avoid broken links.
QGIS just got a missing link point to your file.