Hello Buzz21, The 'Get the desktop app' option should be showing in the Main Company Cog Wheel under the settings column, it will only appear for customers using  QuickBooks Online Accountants and QuickBooks Online Advanced.

Customers that are on Simple Start, Essentials and Plus cannot install the QuickBooks Online app , as it is only  be available to QuickBooks Advanced and Accountants in the main cogs wheel icon.