I have no idea because I have a new policy not to update any Apple or Adobe product for at least three months after commercial release, once there has been enough time for the early adopters to do their QC for them. Systems are just far too varied and complex these days to expect these developers to countenance every conceivable combination of factors that can cause operational problems, and they haven't instituted the extent and depth of pre-release feedback programs that would allow them to much more thoroughly bullet-proof their applications before commercial release. So much to say, perhaps the path of least resistance will be to roll back your Sierra up-grade to El-Capitan and see whether that brings your LR catalogs back to life. Then after all the identified problems get sorted out, retry Sierra. If your photo files also have the XMP side-cars with all your adjustments, that would be added assurance that if all else fails, at least your adjustments are preserved.
