sudo mount -o remount,exec,suid,dev,symfollow /home/chronos/user/Downloads/
You are not able to execute the script since that is "nonexec mount" which means no scripts can be executed from there. To solve this, give your downloads directory exec permissions with the above command.
The above line of code unmounts and remounts your downloads directory with exec and dev permissions so that scripts can be executed from your downloads directory.
The sudo at the beginning is for root permissions, then the remount statement gives it exec, suid and dev permissions and also disables nosymfollow(but that part is optional) and then I mention the name of the directory, which is your downloads.