If check-in staff doesn't give an invitation or if landside check-in is circumvented (i.e., "airside" transits), the OTP lounge staff can fill out an invitation as well -- at least for those whom they know are entitled to access (including all SkyTeam ElitePlus members flying a SkyTeam carrier that day). Presenting the KL (or even AZ) boarding pass and a DL/NW/CO Platinum card (or anyother ElitePlus card) to the OTP lounge desk person will get the person to fill in a blank lounge card with the appropriate details and permit access thereby. It works pretty well.

The lounge can be pretty crowded often enough and the internet PCs don't always work, but it functions and the staff there have been friendly and helpful whenever I've been there lounge card given in advance or not.