"Boot Camp Assistant has encountered a problem An internal error has occurred."

diskutil list

/dev/disk0 (internal, physical):

   #:                       TYPE NAME                    SIZE       IDENTIFIER

   0:      GUID_partition_scheme                        *2.0 TB     disk0

   1:                        EFI EFI                     209.7 MB   disk0s1

   2:                 Apple_APFS Container disk1         2.0 TB     disk0s2

/dev/disk1 (synthesized):

   #:                       TYPE NAME                    SIZE       IDENTIFIER

   0:      APFS Container Scheme -                      +2.0 TB     disk1

                                 Physical Store disk0s2

   1:                APFS Volume Macintosh HD - Data     18.4 GB    disk1s1

   2:                APFS Volume Preboot                 81.7 MB    disk1s2

   3:                APFS Volume Recovery                528.1 MB   disk1s3

   4:                APFS Volume VM                      2.1 GB     disk1s4

   5:                APFS Volume Macintosh HD            10.9 GB    disk1s5

/dev/disk2 (internal, physical):

   #:                       TYPE NAME                    SIZE       IDENTIFIER

   0:      GUID_partition_scheme                        *121.3 GB   disk2

   1:                        EFI EFI                     209.7 MB   disk2s1

   2:                 Apple_APFS                         121.1 GB   disk2s2

Loner T wrote:

On the removed HDD or on the internal disk?

That was on the now removed HDD, the current disk (SSD) has only Catalina on it, no personal files.

I suggest you preserve this backup, till the current issues can be addressed.

Will do!

We need a 'full' installation of Catalina, not a bootable installer of Catalina. If you use Command+R to bot into Local Recovery, we can re-install Catalina on the SD Card. Once we boot from the SD card Catalina, your internal disks can be erased and the Fusion drive can be rebuilt.

That makes sense, I think it's starting to come together what needs to be done. I'll get that going right now.

It is not. Once the Fusion drive is ready, you can re-install macOS Catalina, as shown in How to reinstall macOS from macOS Recovery - Apple Support.

That's how I installed the current OS, I saw the spinning globe so I believe it downloaded and installed it. Somehow it had my wifi password saved from before.

I just came across this How to fix a split Fusion Drive - Apple Support

Is the solution to my problem as simple as following these steps?

So I can't run Boot Camp at all on my new SSD? Do I have any options besides a virtual windows to run it on my machine?

Part of the original fusion drive was corrupted and disk utility couldn't repair it.

I stand corrected. I was under the assumption that the original HDD also had an SSD component built into it which was the fusion disk.

I ran first aid on everything currently installed and it's all ok. The computer ran with the old HDD but it ran poorly and I was unable to install any OS updates and boot camp assistant would not work either.

That is great news that it is possible to run boot camp on the current hardware.

I hate to keep prying but do you mind pointing me toward a tutorial that goes through the process that I need to follow? Currently only the OS is on the SSD so I don't need to backup anything (unless i'm mistaken?).

Thanks for your help!

Yeah I have the original HDD, I've previously formatted it in an attempt to do a clean install of Catalina, which did not work, so I did a time machine restore and put Mojave with all my files back on.

So I also have a time machine backup on an external drive. But it is still Mojave and I'd like Catalina, if possible.

I can use an external HDD to make a bootable Catalina installation if that works? Or I have a 64gb sd card if that would work?

I'd like to do a fresh install of Catalina unless it's too difficult.

Loner T wrote:

Yes, but you may run into a new issue. You now have two SSD disks, not one. The resetFusion seems to barf if it does not see one SSD+one HDD. However, you should try it first, before we go down the manual rebuild path.

Ok I'll make the full install of Catalina on the SD card, then give this a shot. Thanks!