Create a live Linux USB stick and see if the Ubook X still works so far. If so, the SSS is most likely defective.
But this can be fixed quickly. Just buy a Western Digital WD Green SATA SSD 240GB for under 30€. 500GB start at about 40€.
You only have to look for M.2 SATA, not M.2 PCIe NVMe!
You can change the SSD yourself. How you can open the UBook X, I have already shown here in the forum.
After replacing the SSD, you should be able to install Windows again.
Edit: I just saw that you seem to have the UBook XPro. You’d better take a look at the old SSD beforehand. If you google the type designation, you’ll find out whether you need a PCIe or SATA SSD. If you have a normal UBook X, then it is an M.2 SATA in any case.