I had the same challenged, worked with Intuit support with no solution. Ended the session without them being of much help. Even the suggested clearing of the cache will not work. Please follow these simple steps to rediscover Client Requests.

Login to your practice account

Switch accounts to the Client account

Select books review on the left MENU,

The Client request tab should now be available to the right

Select the drop down to create a new request.

Let me know if this has helped you. And QB support should use this for any other Clients having challenges.