An even better option quality wise (many cias on download websites are imperfect dumps) is downloading still direct from Nintendo but from a PC, using for example 3DSeStuff!
The scene generally frowns on video tutorials (and to a lesser extent on written tutorials that aren't Plailect's guide on Github) because they don't keep up with the latest news of the scene, and the video you linked is no exception.
If you use a boot manager as you claimed, you can just download and extract Luma in the root of your SD card, then open your boot manager's menu (usually "boot.cfg") in a text editor, and edit the part that mentions Reinand's .dat file to point to Luma3DS.dat!
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Do you really want to do this?
Just asking because in the "releases" page you can find a precompiled version of the cia, and there have been no updates to the source since that cia was built!
Try removing the battery for a few minutes: if the problem continues you may have a corrupted system configurations (then try a factory reset from the last page of the settings: you will lose all your data if you don't back it up with a save manager), and if the problem still continues, you have defective hardware...
I actually figured it out. I forgot that the battery came out everytime it changed. So everytime I take the battery out, it resets. Thanks though!