When using Internet Explorer, modules are downloaded as a .zip file instead of a .modl file and backups are downloaded as a .zip file instead of a .gwbk file.
When trying to install the module as a .zip, the following error is received:
When trying to install a gateway backup as a .zip, the following error is received:
Change the file extension from ".zip" to ".modl" or from ".zip" to ".gwbk" as is appropriate before installing. Alternatively, you can download the module or backup using a different web browser.
To Change the File Extension (for a module):
You will be asked to confirm that you want to change the file Extension.
Now you should be able to install the module.
If the File Extension is hidden:
You may need to change your settings to be able to see common file extensions. The steps for doing this on Windows is here.