I have a similar issue like this as well with Veeam 9.5 Update 2 and VCSA 6.5D. The plugin installs but when selecting it I get a connection timeout constantly. Tried all things in KB even the cleanup tips.
Case is SR # 02142384 which has been escalated to Tier2.
Chris Childerhose, VCAP-DCA, VMCE9, VCP, MCITP