When attempting to license a user with EMS in Azure AD I hit an error “License cannot be assigned to a user without a usage location specified” when I initiated the license assignment. Googling didn’t initially return a resolution, so here is whats up.
Some Azure tenants require the users profile to have a “Usage location” value when assigning licenses. This instance was a EMS license to a user who’s “Usage location” value was null. Simply input a value and you will be able to assign licenses.
Azure AD -> Users -> Select User -> edit Settings -> select Usage location -> Save
LL&P
Popich
SC Joe 
This error only happens if you assign licences via O365 admin center / License / Assign.
if you go to O365 admin center / active users / more actions / manage product license, it will ask you to select the usage location.
A minor glitch I would say.