This is expected.
Generally, HG2 (Handle Graphics 2) MATLAB releases (R2014b and later) deliberately write graphics objects that might usable in some earlier releases.
However, there was a change in how objects were represented in a release after R2007b, so R2007b is too old to be able to read the file. My memory is telling me that R2010b is the oldest version for which there is a patch which would allow it to read the .fig files without erroring out (though that release might not be able to do anything useful with them.)
If you have access to a release at least as new as you created the .fig in GUIDE, then open the GUI in GUIDE. Then go in to the File menu and use Export. That will create a .m file containing code for the GUI, without any .fig file. You can then edit the code as needed for R2007b (for example if you used ~ in your code to ignore an input or output, then you will need to put in a variable name for versions before R2009b.)
