Hi Ali,
I suggest you reach out to tech support. For example, use the Request Support button on MATLAB's HOME toolstrip.
If you want to explore things on your own, after every step in Fixed-Point Tool, bring the root model to the foreground and perform an update diagram (control-D). This may show you what is going wrong.
If that does not revel the issue, Data Type Override might be hidding issue.
Before doing the update diagram, you could turn data type override ON for each model involved
% mdl is the root model and any child reference models
set_param(mdl,'DataTypeOverride','Double')
Or you may need to turn data type override OFF for each model involved
% mdl is the root model and any child reference models
set_param(mdl,'DataTypeOverride','UseLocalSettings')
Sorry, I don't have enough information on your situation to give more specific suggestions. Hence my initial suggestion to reach out to tech support.
Andy
