I'm installing a new Vcenter server and it needs to be version 5.5. Will a ver 6 license work for that?
yes
Licenses are provided for major versions, so you may need to downgrade the license key in your My VMware portal.
André
Yep, I'm getting "license is not valid for this product". So I guess the license needs to be reordered or changed.
It's actually a self service action. Login to the My VMware portal on which the license is registered, go to the licensing section, select Downgrade License from the dropdown menu, select the license, and follow the steps in the wizard. For details see e.g. https://kb.vmware.com/s/article/2006975
André
sorry, I misread the question. I thought you were asking if a 6.0 license would work for 6.5 not 5.5. As you found out, it won't. You can go to the VMware license portal and downgrade it. But keep in mind that 5.5 goes out of support in Sept on THIS year. You should really be using 6.5 not 5.5.