Thanks for all the responses. I am not sorted yet, but it looks like I need to engage a developer on my side first.
I am unfortunately not a developer, nor do I understand the language. As a result, I would not know where to start looking to change to 777 🙁
Hi Senff. I did exactly that, but no luck. As indicated, the response for .zip upload was that uploaded file could not be moved, while the Add New option ends with message: Downloading install package | Unpacking the package | Could not create directory | Return to Plugin Installer.