Access denied to Reinstall Big Sur

It appears you erased your disk incorrectly. Please follow the steps:

1. Go to Disk Utility.
2. Select "View" in the toolbar —> "Show All Devices".
3. Select your main hard drive or SSD. This will be the top, non indented hard drive. 
4. Click Erase, and input the following exactly: (If you cannot select erase on the main hard drive, erase the "Container" or “Macintosh HD”.)
5. Name: Macintosh HD
6. Format: APFS
7. Scheme: GUID Partition Map (if shown)
8. Click Erase. If “Erase Volume Group” is shown, use that instead. 
9. Quit Disk Utility
10. Go to the reinstall macOS app.
11. Follow the prompts, and install on Macintosh HD.

Cheers,

Jack