On Fleet, this will show as "opted out" under the subscription tab for the individual customer in question. In normal scenarios you will see "enrolled". If they have clicked the delete account option, it will be changed to "opted out". You as a dealer will still have visibility, however, the end user will not have visibility any longer unless the account is re-built. If this is outside of the standard 45-day window that a subscription is returnable, a new subscription will be needed if the customer decides they would like visibility again. The customer would be responsible for paying for a new subscription unless you as a dealer are willing to make a concession and give them a free subscription.
The account delete option is a multiple-step process and does let them know they will no longer have the subscription on their end. Once they confirm they are OK with that, it does require them to type the word DELETE in all capital letters.
First pop-up they receive:
Although this article is for "home sold" scenarios, the process is identical and helps you remove the generator from that deleted account. Click on the article; How to Remove from Deleted Account.
Once you have removed the generator, you will re-enroll it following the standard process by clicking on the +newgenerator option on the FLEET dashboard page.