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Is your Mac connected by ethernet or wirelessly?
did you try a pram reset and start in safemode yet?
Shut down your Mac.
Locate the following keys on the keyboard: Command (⌘), Option, P, and R.
Turn on your Mac.
Press and hold the Command-Option-P-R keys immediately after you hear the startup sound.
Hold these keys until the computer restarts and you hear the startup sound for a second time.
Release the keys.
Then let it try to restart. If it doesnt, shut down the mac after that, turn on, hold down left shift key
for a good 20 seconds to get it to boot in safe mode.
Let me know what happens. We will go from there.
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