Text Disappears when Converting Vector to Shape

After you convert the vector layer to a shape layer, press the U key twice to look for modified properties. I would guess that the text layer was filled with a gradient or had some other clipping mask or effect applied. 

Why are you converting to a shape layer? The only reason to do so would be to use shape layer animators (like trim paths), animate the actual vector path, or extrude the layer. 

If you really need a complex vector layer as a shape layer in After Effects, open Adobe XD, select File New, Import the AI file, and then, before you do anything else, use the File menu to export to After Effects. Ae will open if it is not already open, and every component of the AI file will be a shape layer. Complex Illustrator files become huge messes of nested comps and other funk, but you get a shape layer for everything.