Circle w/ line thru it.
What does it mean, & how can I fix it?
iMac 21.5″ 4K, macOS 10.13
What does it mean, & how can I fix it?
iMac 21.5″ 4K, macOS 10.13
See information in If your Mac starts up to a circle with a line through it - Apple Support
Circle w/ line thru it.