For an overview of the Warning & Error Codes codes have a look here. LINK Updaten
Warning & Error codes are displayed directly in Apexin the Studies tab by double clicking on the Meshless Generative Design Status
Furthermore, you can find warning and error log files - if they occur - in the result folder in your workspace (log_error.log & log_warning.log). The log files are available as soon as a warning or error occurs during the optimisation.