Hi Gamolina
Alas it is a well documented behaviour.
Normally a CS2 start is like this in real time

Notice that adter 55 seconds into the video, a green arrows must appear on the center screen
When it does not then the horizontal progress bar continues all the way to the right.
On my two CS2, one is doing exactly like yours
Initially, by trying many times to reboot, I had it started, managed to have it connected to Märklin for update and check.
So I gained a few month of activity but now it is dead no matter what.

What about Märklin?
- they don't repair the CS2 anymore (no exceptions because according to EU law if the repaired unit fails they must provide a solution (replacement which they can't)
- they propose a rebate on the purchase of a CS3 or CS3+ which usually is less interesting than purchase at a large fealer in Germany (Lippe, etc)

Some specialists say it is about the R/W mass memory which goes out of alternate sectors to replace faulty ones. Some ICs are not available anymore and besides, repairing a mother board costs more than a new one
Here is a 60215 mother board

Cheers
Jean

I hope my CS 3 lasts longer than 10 years. It's not like I use it everyday.

Hi
My only experience on a Märklin CS2 repair by Göppingen was they replaced the entire motherboard of an early 60214 by the latest version of 60215 (5A and galvanic separation).
I suspect repairing would cost more than the automatically-produced brand new one with its automated testing.
Cheers
Jean