Issues with ClickSend SMS plugin

Issues with ClickSend SMS plugin

Hi, 
I'm using the ClickSend SMS plugin in Zoho CRM.  I've connected it to my company account and it works well from the admin account I installed it on.  

however, when I try to run it from another user account, I get an error:


I've given the user access to the module and the buttons on the contact module, but it's not changing their accessibility.

Is there something else I need to perform?

Thanks 

Luke