I checked the switch. When it’s off only one of the cables is live, when it’s one both cables are live. I suspect the cable that goes out of the switch back to the rose is the problematic one but will check this later and if this is the case I will start from the attic.

Have no idea. My wife switched it on and it turned on but flickered for a bit and switched off. No changes have been made and this is the only one that doesn’t work. I already have a good idea what is the cable with the issue. After I confirm it’s the problematic one and find what has happened with it, most probably I will find out why it happened.

Thanks to @Acceptable-Fox-4341 I now know how it works. Not so complicated as you see what is going on. All other lights on this level are working properly. My issue seems to be with the cable that comes from the switch to this rose.

Everything else works except of this one. And as I mentioned I don’t have anything on the Flex L side, so the issue is in the cable that comes from the switch to the lamp - the black one with red sleeve.

Hopefully my internet wiring and bulb have no problems 🤣