Check in the application s folder for " Install Big Sur " application - if it exists ? If yes, drag and drop to trash and empty trash.
Connect to Router via Ethernet connection and restart the computer in Safe Mode and then open the Apple Apps Store and get the Full Installer of Big Sur. It will be the 11.6 version and once downloaded run the installer from the Applications folder.
Should above not bring success >>
Open Terminal Application and cop and paste this command wit quotation marks " softwareupdate -l "It should search for any updates and hopefully present Big Sur 11.6. Not matter , what is important is the output of the search. Now using the results of previous command, the next command, again without quotation marks " softwareupdate --fetch-full-installer --full-installer-version 11.6 " This should bring down the Full Installer of Big Sur 11.6 and during this download will have countdown % until complete. It is of course suggested to be connect via Ethernet Cable to Router for best results and Not be using the computer for another other purposes.
Once 100% downloaded it will Install a New Application called Install Big Sur placed in Applications folder.
