Welcome to the world of SSD... unfortunately SSD failure is more scary than HDD as if often showed no sign of why and when it is gonna happen. I used to had a work laptop which I swapped the HDD with SSD. Those early days low capacity SLC drive with dram cache some more. Even that failed suddenly around a year or so. Luckily I backup everything when it started to hang occasionally whenever I arrived at work (never shut down). I never expected the drive to fail though, therefore I just back those autocad files that I needed just in case. The ssd was only half filled (60GB).

Hmm? Cannot assign drive letter?
You mean you cannot highlight Disk 3 Partition 1, right click, select Change Drive Letter and Path and assign a drive letter directly?