Permission denied enabling/starting script

From SSH I get the following error:

root@OpenWrt:/etc/init.d# /etc/init.d/startup-script enable 
-ash: /etc/init.d/startup-script: Permission denied

I had logged in before and I can use commands like cp in the directory without problem. I get the same error with start and LuCi shows the following message: Failed to execute "/etc/init.d/startup-script enable" action: Command failed

I was following the guide of this post, with a few changes to the filenames and a portion of the first script so I could check the connection to the main router in the LAN network. I am having trouble with the second script file, which is /etc/init.d/startup-script.

Do you know how can I solve it? I've googled and found nothing.

Thanks in advance.