iMac 2019 will not boot up. Ran Disk Utility and did first aid on all drives. Still won’t reboot. Cycles through loading and then showing this screen. Tried to reinstall OS and not enough space. Tried to install backup and it says to update OS. Tried plugging in an external Portable SSD (T7 2TB) to try to load the OS but will only recognize the hard drive which doesn’t have space. What now!!!!
iMac 21.5″, macOS 15.3
That's a kernel panic, which is usually an indication of a hardware fault: If your Mac restarts and a message appears - Apple Support
It sounds as though you're stuck. Having done everything else, did you try completely erasing the startup disk, using Disk Utility in Recovery mode?
Use Disk Utility to erase an Intel-based Mac - Apple Support
Erase it, and then you might be able to successfully reinstall macOS. You will want to be certain your backups (plural) are viable restore options, but from what you describe there may be no other choice than to erase the Mac anyway.
That's a kernel panic, which is usually an indication of a hardware fault: If your Mac restarts and a message appears - Apple Support
It sounds as though you're stuck. Having done everything else, did you try completely erasing the startup disk, using Disk Utility in Recovery mode?
Use Disk Utility to erase an Intel-based Mac - Apple Support
Erase it, and then you might be able to successfully reinstall macOS. You will want to be certain your backups (plural) are viable restore options, but from what you describe there may be no other choice than to erase the Mac anyway.
Please take the computer to your local Apple Authorized Service Provider to be professionally diagnosed and then you can decide on a course of action. If you take it to an Apple Store they do not charge for diagnostics and if it requires repair they will quote the amount so you can decide.
Kernel Panics are extremely difficult to diagnose because they can be caused by software or hardware and in rare cases both. Hardware includes external peripherals too, if one has failed or is woefully out of date that can cause a KP. The same thing with software, if you have third party software installed and have not updated it regularly then this can be a cause of KPs.
On the computer, RAM is a frequent cause of KPs. If you ever updated the RAM and installed ANY but Crucial.com or OWC (www.macsales.com) RAM then that is a great place to start. iMacs are extremely sensitive to RAM and demand using very high quality RAM, both Crucial.com and OWC meet those needs. Note, if you installed Crucial RAM and did not buy it directly from Crucial that could be an issue.
Also, if you installed any of the following types of third party apps those are MAJOR trouble makers:
I ran Apple diagnostics and it didn’t show any hardware issues.
... which is the reason I did not recommend doing that.
iMac 2019 will not reboot, can’t reinstall OS because not enough space.
