Hi,
Thank you for posting in Symantec community.
The Endpoint Protection Small Business Edition 12.1.x product has reached End-of-life and is set to be replaced by the Hosted (or .Cloud) version of the product.
Note: This does NOT mean the customer needs to immediately upgrade their product. Customers will be able to renew their on-premises license and continue to use their SBE SEPM’s until 2018.
& SEP enterprise edition and SEP small business edition can stay in the same network.
Upgrade from SBE to EE is also supported. Can refer this article: Supported upgrade and migration paths to Symantec Endpoint Protection 12.1.x
https://support.symantec.com/en_US/article.TECH163514.html
How to upgrade/cross-grade Symantec Endpoint Protection 12.1 from Small Business Edition to Enterprise Edition
https://support.symantec.com/en_US/article.TECH166993.html
Upgrade or migrate to Symantec Endpoint Protection 12.1.6
https://support.symantec.com/en_US/article.TECH230601.html