I am really glad to see you got it worked out. I had just been typing an email up to you. Below is the body of that email just in case others see this issue in the future.
java installed on the system should not matter, as the application bundles
our own java. It may be that for some reason there was a failed install,
and trying again might help.
and perhaps more helpful, according to the system requirements for 5.4 it
is fully supported on Windows 11 provided it is a 64bit OS: https://education.ti.com/en/products/computer-software/ti-nspire-cx-cas-student-sw?category=specifications. We have seen a similar Java error caused
by permissions so [Right-Click] [Run As Administrator] of the program
shortcut may be all that is needed to workaround that error.
If you’re still having issues, I would suggest reaching out
to TI-Cares via email: https://education.ti.com/en/forms/global_forms_customersvcform
or phone call 972.917.8324
Happy to help if I can, but the folks in the customer service
group are really awesome!