I only briefly put the batteries in to test whether they were working. One shows that the battery is almost full and one it flashes red. Just the battery almost empty or is there something else behind it? A battery cost almost 16 EUR and they also had reasonably good reviews. Of course, as with every product, there's one or the other who is not satisfied, but it is the same everywhere. Better than sending it to Nintendo.
It can of course be empty, for whatever reason. Try charging it first. If it is then quickly empty again one can assume that you have been accused of a defective battery. Would be a reason for a complaint. With the other you have a battery to compare. Note the complaint times.
