My Mac book won’t start after update. I get a flashing” ? “ With support requested
My Mac book won’t start after update. I get a flashing” ? “ With support requested
MacBook Pro 13″, OS X 10.10
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Start here:
https://support.apple.com/en-us/HT204323
Follow each individual link (eg NVRAM) within the document. I've had NVRam issues in the past re non silicon chip devices, so hopefully yours is as simple.