When a customer gets an "invalid tokenization" error on a Clover device, this is because EMV tokenization is not enabled on their Clover Device.

Conference in Clover and ask them to enable EMV Tokenzation on the device. 

Once enabled, it will not work right away. Clover pushes updates to all machines between 5-7pm, so if it's before this time it will work after this window. If it's after this window, it will take until the next day before it will begin working.