Reset mac -- can't reinstall macOS
Yes. Be sure you erased the entire drive from recovery. Some people erase only a volume and get stuck, the entire drive should be erased for your downgrade to work the fastest.
Which of these keys are you using?

https://support.apple.com/en-us/HT204904

For your case, you want Shift-Option-⌘-R

Reinstall the macOS that came with your Mac, or the closest version still available.