It's possible the replacement hard drive cable could be bad - I remember I ordered 5 of them once and 2 of them were dead on arrival.
Either that , or the hard drive itself requires replacement.
The flashing folder happens when the MacBook can't detect the operating system. If you have installed a new ribbon cable but the hard drive has failed, or a new hard drive but have not reinstalled the operating system, you'll see the flashing folder.
Easiest way to check would be to boot into either Recovery mode or off an install USB if you have one and load up Disk Utility.
If the hard drive appears and you can run First Aid on it and it passes, the drive should be fine.
If the hard drive doesn't appear when connected to the ribbon cable but does appear when connected externally, your ribbon cable is probably bad.