Failed to execute git checkout 'a91aebfe2184f3f032943c541cc65a31f5c3fe88' -- && git reset --hard 'a91aebfe2184f3f032943c541cc65a31f5c3fe88' -- fatal: reference is not a tree: a91aebfe2184f3f032943c541cc65a31f5c3fe88 It looks like the commit hash is not available in the repository, maybe the commit was removed from the branch? Run "composer update wporg/wporg-mu-plugins" to resolve this.