Hi, good day!
Please try to check your Microsoft order history first for any pending or incomplete transactions. If you find one, cancel it or wait for it to expire, then try purchasing the Windows 11 Pro upgrade again.
https://account.microsoft.com/billing/orders
Reset the Microsoft Store cache using wsreset.exe, then try the Windows 11 Pro upgrade again.
Press the Windows Logo Key + R to open the Run dialog box,
type wsreset.exe -i
and then select OK.
Note:
A blank Command Prompt window will open, and after about ten seconds the window will close, and Microsoft Store will open automatically.
After that, try the upgrade again immediately
I look forward to receiving your update and I'm willing to collaborate with you till we resolve the issue. Do keep me informed by clicking "Add comment" below.