VMWare support informs me that my two vCenter's are in linked mode which is no longer supported. (Funny how the option was there.)
Content Library worked prior to recent VCSA update (as far as i can tell).
Now I have to magically unlink them which seems not even possible unless i purge one of the vCenters and re-install from scratch.
I have the same situaltion, but i have only one VCSA.
I'm also having the same problem, but it was working before which leads me to believe a patch maybe broke something. Are we all running VCSA 6.5? We started with a fresh 6.0 install and upgraded to 6.5.
Nevermind, I believe I have found a fix for my problem which may also help the others having this issue.
A blogger posted a message for what seemed like a similar problem: https://notesfrommwhite.net/2017/08/01/cant-create-a-content-library/
And he referenced this VMware KB article: OVF deployment fails after upgrading to vCenter Server Appliance 6.5 U1 (2151085) | VMware KB
He was correct in my case in that all that OVF stuff wasn't applicable. Just follow the 1-8 steps and try starting the Content Library Service. It should work.
A little maneuvering might be required if you manually deleted the content library files off the datastore as I did, because the VCenter database will still think one is there and will show it in the GUI. So what I did was rename the library which will recreate the "contentlib-<hex num>" folder under your datastore. Then delete the content library. Hope this helps!