Most likely you have not selected the machine file type that you want to open.
If you are opening your designs using the File Menu:
If you are using File > Open design, you should select the specific stitch type
If you have multiple stitch types, you may want to select "all embroidery files" so that you can see all the designs at one time.
If you are opening your designs using the Design Manager Toolbox:
If you are using Manage Designs, they will be listed as "Showing"