Hello,
I would suggest you to delete all the Licenses from the SEPM (including Trial License, if any) and upload the latest .slf license again.
Secondly, Have you seen this:
After installing a Symantec Endpoint Protection 12.1 client, you receive a warning that the trial license has expired even though the SEPM has an active non-trial license.
http://www.symantec.com/docs/TECH171252
Here is a good quick guide on SEP Enterprise Edition 12.1 licensing:
https://www-secure.symantec.com/connect/sites/default/files/SEP%20EE%20Licensing%20guide.pdf
This illustrates what to expect with SEP 12.1 licensing on both the server and client side. I forgot to mention the part about submissions to Insight with an expired license.
Secondly, Check this Article: https://www-secure.symantec.com/connect/articles/sep-121-and-license-concept and check the Attachments for clear understanding.