Chosen Solution
After replacing the stock 500gb hard drive with a 500gb Kingston SSD and replacing the hard disk cable I’ve ran into some problems. Sometimes the computer won’t boot up, it sits on the screen with the line through the circle and after about 10 seconds it quickly flashes an apple logo like it’s going to boot up but then goes back to the circle logo. It keeps doing this every 10 seconds until I turn the laptop off. Sometimes however if I leave the laptop to sit for 20 seconds on that screen it will actually power on but I can’t figure out what is causing the problem. Also if I close the lid after its booted up and let it sit for maybe 20min or so when I open the lid the display won’t turn back on however the apple logo on the back and power light is still on so the laptop is still on but it won’t wake from sleep too so I have to restart the laptop but then it won’t boot up and so I have to hope it will turn back on or I have to let it sit for 10 minutes and hope it will turn back on after because sometimes it boots it I let it sit powered off for a bit. Please reply ASAP as I need this for school
First thing to try is selecting the Boot Drive: Under the Apple > System Preferences > Start up Disk > unlock it and select your drive. Then try rebooting.
