only 24Hz or no signal or connector defective

For the price and the claim to be OEHLBACH is here this cable is unfortunately an indictment.
This is very thick and stiff, the line is logic in multiple shielded cable with thicker wires,
the plug is almost twice as long as that of comparable DP cables and the lock can be released only with great difficulty and thereby breaks like, do not.
To a non-active DisplayPort cable you need the full bandwidth of DisplayPort exploit (HBR).
Unfortunately, it creates this cable (7.5m version) not, my not clean to recognize let alone conjure 120 / 144Hz on the screen, so usually the cable even lose the signal to the monitor Asus PG278Q (2560x1440 @ 144Hz).