Do not buy new hardware
Go to this community forum and you will find the answer you are looking for.
Basically what happened is, when you first secure-shelled into umbrel you typed ‘yes’ to a question. That question asked if you wanted to add umbrel to your computer’s list of known hosts. Now that you reflashed umbrel your computer sees a dif file and thinks something is up. I had the same issue.
I am on a Mac computer, so not sure about Windows (if different), but you need to remove umbrel from your known host file. Just go into terminal/powershell (of your comp, not umbrel) and type:
nano ~/.ssh/known_hosts
That will bring you to a primitive looking text editor that looks like this:
Delete all of the text in the umbrel.local section, and then press control+x to exit and then y when it asks you to save, and then enter key.
You can now ssh back into your umbrel because you don’t have a conflicting known host file.