When I turn the power on to start the operating system to load it loads till about 90% and then stops. I don’t see any menu items and I don’t have any means of logging in. These are the two symbols I see interchanging regularly.
Those symbols mean that your iMac is looking for the wireless keyboard and mouse.
If you can't connect your Magic Keyboard, Magic Mouse, or Magic Trackpad to your Mac - Apple Support
If you have the newer rechargeable magic keyboard and mouse..?
Try turning them off and then back on. If that does not help. plug the keyboard into to computer and plug the mouse in for 10 minutes then unplug.
If you have the older AA battery power keyboard and mouse..?
Dig out, borrow or buy a USB keyboard and mouse. Plug those into the iMac. then use them to login and reconnect your AA battery powered keyboard and mouse.
Those symbols mean that your iMac is looking for the wireless keyboard and mouse.
If you can't connect your Magic Keyboard, Magic Mouse, or Magic Trackpad to your Mac - Apple Support
If you have the newer rechargeable magic keyboard and mouse..?
Try turning them off and then back on. If that does not help. plug the keyboard into to computer and plug the mouse in for 10 minutes then unplug.
If you have the older AA battery power keyboard and mouse..?
Dig out, borrow or buy a USB keyboard and mouse. Plug those into the iMac. then use them to login and reconnect your AA battery powered keyboard and mouse.
It looks like it's expecting to load the OS from an external drive. What exactly did you do when you "ran filevault"
I ran File Vault On my iMac and now it won’t load
