If a client purchases a pack and needs to move the pack to a different client, what you can do deactivate the pack, add account credit to the second client's profile, and purchase the pack with the account credit.
Currently, there is not an official way to transfer a pack or plan to a different client.
Go to the client's profile that purchased the pack
From the Active Plans section, choose the three dots on the top right of the plan tile
Select Deduct Passes and enter the amount of passes remaining as well as Adjustment name or reason so the total pass count is zero
Select Deduct
Select Buy and choose Plan
Search and select the client's name you want to "transfer" the pack to
Choose the pack you want to add to the client's account
Select Continue
Choose Apply Promo or Discount
Enter 100% and choose Save
Select Buy
You will now see the pack added to the client's account!