Bootcamp no longer sees my internal 2.5" SATA SSD

It seems either Bootcamp and/or Windows have been updating themselves a lot recently... in the last ~4 months (give or take a few months). I only realised this week that my 2TB internal storage drive is no longer visible. It's formatted as an NTFS drive (I think). I have windows loaded onto the blade-style of SSD. No problem with that. It is Windows 10. 2014 retina 27" iMac. I vaguely remember I had this problem before when I first bought the 2TB drive and installed it. It was plugged in but windows could not see it. But I can't remember what I did to get it to appear. Maybe it was something to do with with AHCI. Or maybe not! I am not seeing any "IDE ATA/ATAPI controller" in the device manager (and no other errors there either) I could really use some help in figuring this problem out.