Communication problem with arduino uno and simulink

My project entails a smart grid controlled by an arduino to a gps device, however i am having an issue with the programming from simulink to arduino. The arduino should act as a monitor for voltages from pv and a switch to turn off renewable but an error loop is given is there a simpler way to get this done?

No code, no schematic, vague description of the problem. Mention of an error, but no error message posted. Is there a simpler way? Who knows.

Please read the "how to use the forum" stickies to see how to format and post code and error messages. Also some hints on how to ask effective questions.

This is what i have currently as i am in initial stages of testing

Still no code

This is an Arduino forum. Although there may be someone here that can help with a Simulink problem you are more likely to get answers on a more appropriate forum.

ok will post else where thanks