I'm assuming that you are using MATLAB R2020b or R2021a. The error you are encountering is likely a connection error during XCP external mode simulation due to a DWARF parser internal error. This issue is documented in an external bug report, which you can view here: https://www.mathworks.com/support/bugreports/details/2558824. You might find the workaround provided in the bug report helpful. The issue has been resolved in MATLAB R2021b, so updating to this version could be a solution if needed.
Additionally, you can check out this MATLAB answer for other possible workarounds: https://www.mathworks.com/matlabcentral/answers/703597-dwarf-parser-internal-error-parser-describesymbol-xcpdummydoublevariable-is-not-a-global-variable.
Hope this helps!
