Problem:

When upgrading Update Manger from 5.5 to to 6.0.0 U2 on a new windows machine:

Error 25085. Setup failed to register VMware vSphere Update Manager extension to VMware Vcenter Server: 

 

The installer rolled back.

Looking in the logs vminst.log file located in  %Temp%

VMware Update Manager-build-3545890: 02/23/17 10:49:25 INFO: Reg/UnReg extn command: ["-v vc.jordansphere.co.uk -p 80 -U "[email protected]" -P *** -S "C:\Program Files (x86)\VMware\Infrastructure\Update Manager\extension.xml" -C "C:\Program Files (x86)\VMware\Infrastructure\Update Manager\\" -L "5tULkd$g\" -O extupdate"]
VMware Update Manager-build-3545890: 02/23/17 10:49:25 AppendPath::done Path: C:\Program Files (x86)\VMware\Infrastructure\Update Manager\vciInstallUtils.exe
VMware Update Manager-build-3545890: 02/23/17 10:49:25 Found "C:\Program Files (x86)\VMware\Infrastructure\Update Manager\vciInstallUtils.exe"

VMware Update Manager-build-3545890: 02/23/17 10:49:31 Process returned 255
VMware Update Manager-build-3545890: 02/23/17 10:49:31 Error:: Other runtime error
VMware Update Manager-build-3545890: 02/23/17 10:49:31 ERROR: VUM registeration with VC failed
VMware Update Manager-build-3545890: 02/23/17 10:49:31 Posting error message 25085

 

Resolution:

Looking that the "-L "5tULkd$g\" error highlighed above it appears that this was only partially showing my password for [email protected]. It appeared anything before a semi-colon was removed. To get around this I created a new user (which I should have done in the first place) called [email protected] and created a password without a semi-colon. It re-installed successfully this time.