Sounds like you need to reinstall the operating system.
I would turn it on and as soon as it turns on try this:
1. Hold down the Command Key & the “R” key @ the same time. Wait till recovery mode shows up and follow the instructions from there on to install the new OS.
2. Hold Down the Command + Options + R Keys at the same time this is for Internet Recovery mode.
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3. Try resetting your PRAM by pressing and holding the Command + Option + P and R keys right as you turn the computer on and wait for the computer to restart on its own and chime once again then let go.
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4. Try resetting your PRAM by pressing and holding the Command + Option + P and R keys right as you turn the computer on and wait for the computer to restart on its own and chime once again then let go.
Sounds like you need to reinstall the operating system.
I would turn it on and as soon as it turns on try this:
1. Hold down the Command Key & the “R” key @ the same time. Wait till recovery mode shows up and follow the instructions from there on to install the new OS.
2. Hold Down the Command + Options + R Keys at the same time this is for Internet Recovery mode.
3. Try resetting your PRAM by pressing and holding the Command + Option + P and R keys right as you turn the computer on and wait for the computer to restart on its own and chime once again then let go.