I experienced the same problem. Kuri0 shared this https://www.reddit.com/r/hackintosh/comments/jw7qf1/haswell_asus_z97_big_sur_update_and_installation/
In my case, Asus updated the BIOS(starting with October 2014) and blocked new uefi variables with the exception of an allowed list(likely for security reasons). That is preventing ReBarState to write the new variable. There are two options to fix this:
- add the ReBar variable to the allowed list(this is the ideal solution). A patch is required.
- download an older BIOS for your motherboard, extract(as is) the NvramSmi module using UEFITool and replace(as is) this module with UEFITool in your current BIOS.
I tested the second option and it works for me. But without the allow list, potentially any application with admin rights can store persistent data in nvram, hence the security concern.