Thought I'd post this in case others are looking for a resolution to the error I received. In my testing of XO/XCP thus far, I hadn't yet implemented AD-integratin (LDAP)....until today. I wanted to test this out. I was entering the parameters as I found in the KB:
https://docs.vates.tech/kb/vkb-1166/
as well as the User Guide:
https://docs.xen-orchestra.com/users-and-access/users#ldap

...but was still running into "Could Not Authenticate User" error when I went to 'test' the plugin. I knew the pwd was correct as I logged into other systems with this acct. I tried other accts, and multiple LDAP servers (DCs), and even took DNS out of the equation (used IP)...as well as not checking for certificates. Nothing. I ended up changing one of the parameters that finally got me a successful test ---> the "User Filter" parameter. I had "(sAMAccountName={{name}})" in the configuration box and decided to change it to "(userPrincipalName={{name}})" which ended up being the the change that got me going. Aside from helping others who may experience this issue, I'm also posting for Olivier and the Vates team to see if there's a way to have a more precise log event pinpointing to the problem section in the plugin to help troublehshoot? Not sure if it's possible...but thought I'd put my feedback here as well.
Thanks Community!