We just upgraded to this version as well on our manager. In the process of upgrading, I am upgrading the tools to the same version as you, but the appvolume agent cannot contact manager whenever I use that version of tools. Curious if you would be will to test updating the tools, if your environment allows it?

EDIT: FYI - I just tried to install my agents, starting with VM Tools 11.1.0 and App Volumes 2.18.4 and I have no error messages contacting manager.