I have a 27 inch iMac (late 2015) It’s running High Sierra version 10.13.6
It will not shut down unless I hold in the start button for a few seconds. It started doing this about two months ago. The storage capacity was almost full. One day i got on it and mail and messages wouldn’t work. I was no longer signed into the accounts. Photoshop cs6 and Wacom tablet that was installed had reset to factory settings and lost all of my actions. And my computer would no longer shut down. Screen just goes black and the cursor moves to upper left corner.
I have logged back into messages, mail accounts, reset everything in photoshop and on my Wacom tablet, and moved stuff onto hard drives so that I freed up half the disk space. iMac still won’t shut down.
i have tried all the usual suggestions. Run disk utility, unplugged power cord, started in safe mode, reset smc and nvram. What else can I do?