To update to latest luma you actually must be on the latest bootsratp9 version.
Supposing that you are in A9LH (sorry, I couldn't understand properly your OP) you must perform the steps in this section of the guide:
https://3ds.guide/a9lh-to-b9s
If you don't want to update from A9LH to B9S, you should use this version of luma (that may be older than your Luma if you used nightlies through luma updaters)
https://github.com/AuroraWright/Luma3DS/releases/tag/v7.0.5 by simply replacing the arm9loaderhax.bin file of your SD card with the one contained in the 7z file.
edit:
-ed