While upgrading to ITMS 8.6, the following error message was displayed, causing the upgrade to not start:
Symantec Installation Manager
You have selected an unsupported product version '8.6' for upgrade.
Select an appropriate product version to proceed with the upgrade.
Check the supported upgrade paths in help.
ITMS 8.5 RU3
In this particular case, the currently installed version was ITMS 8.5 RU3, which is not supported to upgrade directly to ITMS 8.6 or 8.6 RU1
The following are the supported versions for upgrades to IT Management Suite (ITMS) 8.6 and you can upgrade from the previous versions of ITMS to the latest version using Symantec Installation Manager.
ITMS 8.6 General Installation and Upgrade Information (broadcom.com)
Supported upgrade scenarios:
8.0 > 8.0 HF6 > 8.5 > 8.5 RU4 > 8.6 > 8.6 RU1
8.1 RU7 > 8.6 > 8.6 RU1
Supported migration scenarios:
1. Apply IT Management Suite 8.0 HF6
2. Upgrade to IT Management Suite 8.5
3. Apply IT Management Suite 8.5 RU4
4. Upgrade to IT Management Suite 8.6
1. Apply IT Management Suite 8.1 RU7
2. Upgrade to IT Management Suite 8.6
221113 "You have selected an unsupported database version '8.5 RU4, 8.6' for upgrade"