iMac won’t start up

Hello, DannySpurs.

Please take a look at this support document –

If your Mac doesn't start up all the way - Apple Support:

https://support.apple.com/en-us/HT204156

Also this –

If your Mac starts up to an Apple logo or progress bar - Apple Support:

https://support.apple.com/en-us/HT207019

Then it is possibly a hardware issue. You can attempt to restart in Safe Mode (Use Safe Mode to isolate issues with your Mac ) and also attempt to restart into the Recovery Volume by holding down Command + R on start up, open Disk Utility and run First Aide on the startup drive. If any errors are found (best to run First Aid about 3x) then you know the startup drive is damaged and should be replaced. If it will not start in the Recovery Partition, it's definitely a hardware issue.

You may want to consider taking it to your local Apple Authorized Service Provider. Apple Authorized Service Provider Locator (AASP) & Genius Appointment

Your welcome, By the way if it's older than a 2013 or 2015 it's obsolete anyway.