Access rights are not granted with .FullAccess

Hello,

I have a robot with the following code to write in a file :

        protected override void OnStop()
        {
            string filePath = "C:\\Users\\Windows\\Documents\\cTrader\\Watcher\\" + Symbol.Code + " save";
            using (StreamWriter saveWriter = new StreamWriter(filePath))
            {
                for (int i = 0; i < horizontalLines.Count; i++)
                {
                    string line = "Y" + horizontalLines[i].Y + "A" + horizontalLines[i].A + "R" + horizontalLines[i].R + "G" + horizontalLines[i].G + "B" + horizontalLines[i].B;
                    saveWriter.WriteLine(line);
                }
            }
        }

If I give him no access he crashes OnStop because of the StreamWriter :

[Robot(TimeZone = TimeZones.UTC, AccessRights = AccessRights.None)]

If I give him full access or filesystem access he does not run :

[Robot(TimeZone = TimeZones.UTC, AccessRights = AccessRights.FileSystem)]

[Robot(TimeZone = TimeZones.UTC, AccessRights = AccessRights.FullAccess)]

I get the following error when I try to start it :

17/04/2019 11:10:10.040 | Watcher, USDCHF, h4 | Access rights are not granted.

Can you please tell me why this happens ? 

Thanks.