The licenses are different and can't be used together.

We spent quite awhile working on this ourselves and eventually had to get our reseller involved to get an escalation with the people in licensing.  After all that I'd start there.  If you can't or don't know who that is you can always try calling the helpline listed in the license portal.  Hopefully you won't run into the issues we did.

I'm dealing with this right now, and my reseller and his contact both assured me that the Servicedesk licenses will work.  I'm not going to try replacing my existing licenses with the Servicedesk ones.  Instead, I e-mailed support, requesting Helpdesk licenses, but have not heard back.

I've had horrible luck with licensing@symantec.com.

Thanks for your response. I will contact my reseller, since I also have had bad luck with Symantec customer support before.

Went through this last July.  When we renewed our licenses for this fiscal year, we were sent a ServiceDesk 7.0 license file and we are still using HelpDesk Solution v6.0.  You will not be able to install ServiceDesk 7.0 license file on HelpDesk Solution v6.0.  What you need to do is call License support and request for a downgrade license file.