Upgrading CUCM from 9.1.2 to 10.5 – Issues

Hi there, today I have a customer that wanted to upgrade from CUCM 9.1.2 to 10.5 - which sounds pretty easy… think again, so this is a BE6K deployment where CUCM instance was configured with the recommended OVA from CCO. When starting the upgrade I found that the upgrade didn’t wanted to proceed as expected. and I was getting the following error: Installation of UCSInstall_UCOS_10.5.1.10000-7.sgn.iso failed An error has occured but no messages are available. This can happen when another administrator is working on the system at the same time and triggers an error.