So.... I decided to self install a new SSD on my 2015 iMac. It greatly improved my speed and functionality. Until... one day the iMac would not boot up. Command + R doesn’t work. Just a black screen. I can’t get it to boot up. If I leave it on long enough it will show a question mark in a folder.

Can you help me get it running again? I do t have anything on the HD that I am worried about losing. I just want it to access the internet and connect to our I drive.
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Sorry to hear the iMac isn’t booting. First thing to check is the connecting cable to that internal SSD drive. Sounds like it’s either come loose or there’s an actual problem with the drive itself. The folder icon means either it can’t find the OS or it can’t find the hard drive the OS is installed on. If you want some extra credit, here are a few ways to troubleshoot the issue:

• Boot from a known good version of the OS that you’ve installed on an external drive. Then wipe and reinstall the OS onto the internal drive.
• Remove the internal drive, use an enclosure and reinstall the OS from a different computer.
• Remove the internal drive and boot the computer using another computer in target disk mode.
• Remove the internal drive, put it Ito an enclosure and try to boot a different machine from that HD.

Sounds like the issue is the OS install on the internal drive. I bet you can bring it back to life. I doubt that it’s hardware on any other part of the machine.

If neither of those are an option for you, I'm happy to pick it up and see if I can bring it back to life.