I have a 2018 15in macbook pro but am stuck on Catalina 10.15.7. When I go to and check software update, it says that my mac is already "up to date". I then go to App Store to try to download Big Sur. But it says "Update not found. The requested version of macOS is not available".
I've tried restarting my laptop, tried checking in recovery mode, and disabled VPN. None of those work. I also check to make sure i have enough storage as i saw some people mentioning that can be an issue. But I have over 200gb of storage remaining. So I'm not sure what else to do.