Spinning coloured wheel

If you're able to boot up your Mac and get on it download and run Etrecheck. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support  to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

IMPORTANT:

Before running Etrecheck assign Full Disk Access to Etrecheck in the Etrecheck's Privacy preference pane so that it can get additional information from the Console and log files for the report:

Also click and read the About info to further permit full disk access.

Copy the report

and use the Additional Text button to include the report in your reply.

Then we can examine the report and see if we can determine what might be causing the problem.

It is because the computer is unable to find an operating system to start up. Have you done anything or changed anything? Try starting up from the Recovery Mode - hold down the Command + R keys on startup. Then run Disk Utility to see if it can be fixed. If not, then try reinstalling the OS. You may have to restart in the Internet Recovery Mode to do this. Hold down the Command + Option + R keys on startup. That will reinstall your original OS. If you were running a later one, you will then have to do an upgrade. If nothing works, then that would indicate that your hard drive has failed. You have told us nothing about your computer or how old it is, so that is all I can offer.

Hi andyroy3,

Do you mean you can still use the computer, but you see the "Beachball" sometimes, or it is unusable with the "Beachball" and nothing is happening?

Cheers,

Jack