Read and work with tif DTM

I'm using Matlab 2017a with Mapping Toolbox. I have a DTM (elevation of terrain shown a gray scale) as a .tif file (the file was produced using arcMap so it contains all the geographical data needed), i tried using the geotiffread function to read the file and then use the geoshow but i keep getting an error that "Valid colormaps must be nonempty, double, 2-D matrices with 3 columns"

iv'e tried following the help for geotiffread & geoshow, and the example shown but i just keep getting the same error

what am i doing wrong? i also tried: 1. using the mapshow 2. converting the data to double from single