Same experience as several others. I have logins for Lufthansa, Swiss, Austrian, and Miles-and-More. All more-or-less linked together as the Lufthansa group companies have been for some years.
I received the Swiss-branded "Travel ID is coming" email. I stupidly followed it.
The result is a brand new, empty Miles-and-More account, which has been overlaid onto my existing Lufthansa ID (and now Travel ID).
The old Miles-and-More account is still there, and I can still log in to it using the Service Card Number and PIN.
I sent a web form to Miles-and-More asking them to remove the new, blank, unneeded Miles-and-More account and to re-link my old, existing, correct Miles-and-More account to my Lufthansa/Travel ID. (*chirping crickets in the dark*). No reply.
A week later I telephoned the Miles-and-More "service centre". They can't do anything with it, except send it to their "back office" (which is what has been sitting on my earlier request).
As others have said, Lufthansa does many things right, but I.T. is absolutely not one of them. Nor is overall business process testing, nor especially customer servicing business process design and execution. The "firewall" that exists between anyone-we-can-talk-to and anyone-who-can-actually-do-something is horrific.