From Symantec Endpoint Protection Manager (SEPM) when clicking Reports > Quick Report > Computer Status > Symantec Endpoint Protection Product Versions, you get a report you can click the server name to get more details, this opens up another report with the title "Out of Date Clients for Server <SEPM name>". In an environment with only 12.1 clients it always shows 0 clients, even if there are clients with older product versions.
Working as designed.
For Symantec Endpoint Protection Product Versions report showing out-of-date, the code looks for the client that has the highest major and minor version combination in the database and will call that the latest Symantec Endpoint Protection (SEP) version. For SEP 12.1, the major version is 12 and the minor version is 1. Any client with a major version less than the latest major version, or any client with a major version that is the same as the latest, but whose minor version is less than the latest are considered out of date.
As such, any 12.1 clients in a customer environment will be identified here as out of date provided at least one SEP 14 client is also present. If the customer only has SEP 14 clients in their environment, there will not be any clients listed here as none meet the criteria.