Client: PC
Version Info: 2023.31.0.4709.1039979

Purchasing the mastery pass with gems does not unlock the mastery pass. If you attempt to purchase it again, you receive a message regarding a store error.

"Store Error
Quantity is over the maximum for your account"

Steps:
Log into the PC client for MTG Arena
Click on Mastery in the top navigation menu
Click "Unlock Mastery Pass" in the bottom right-hand portion of the screen
Click the option that costs 3400 gems
Note the mastery pass isn't unlocked

I have attached the log file, a screenshot of the error, and a screenshot of the mastery path still being locked post-purchase.

Workaround:
Reload the client and the mastery path properly shows as unlocked.