Bootcamp - "The bless tool was unable to set the current boot disk" ?

Today when I tried switching to my Windows 10 Bootcamp drive I got the error "The bless tool was unable to set the current boot disk."

Nothings changed except I did notice an MacOS update message last night but just clicked it away so not sure what was updated.

If I try and boot into windows using startup the bootcamp drive doesn't appear. If I start the bootcamp assistant the only option I get is to erase the bootcamp drive.

Any ideas? Any way to manually bless?

Thanks.