Run Disk Utility First Aid on the hidden Container. Within Disk Utility you may need to click "View" and select "Show All Devices" so that the hidden Container appears on the left pane of Disk Utility. Even if First Aid says everything is "Ok", click "Show Details" and manually scroll back through the report to see if there are any unfixed errors listed. If there are any unfixed errors listed, then you can try running First Aid while booted from Recovery/Internet Recovery Mode or a Big Sur USB installer, otherwise you will need to erase the whole physical drive (Intel only) and restore from a backup or clone. If you have an M1 Mac, then you can try following the instructions in the Recovery Mode links or you may need to "Restore" the firmware since I'm not sure Apple's method will reformat the entire Container required to eliminate the unfixed errors.
What is the exact model of the Mac? You can get this information by clicking the Apple menu and selecting "About This Mac".
Also what is the exact error message you are receiving when attempting to install Big Sur?