Looking it up, this appears to be a 24mm FSA Mega Exo crank that presumably uses square-edged splines of some sort.
If so, the first thing to look at is the spline interface on the drive side cranks. Cranks of this sort have very little tolerance to damage to the splined interface. Any rounding, mashing, distortion, etc, and the crank is toast. Usually, repeat issues with loosening mean that's exactly what you're going to find there. The system relies on a press fit in the splines such that there's no movement in them when riding. If you do find that kind of damage, and it's really only been barely ridden, it's likely the crank bolt was under-torqued initially and/or the crank bolt wasn't lubricated properly.
Limping along a crank with these issues by using threadlocker and/or extra torque on the crank bolt doesn't usually succeed in addressing the movement happening in the splined interface. It may help for the very short term but the usual pattern is the problem will just get worse. Warranty or replacement are what you're really looking at if the splines are damaged.
If by some chance the splines are not damaged, then clean and grease them thoroughly, grease the crank bolt shoulder and threads, give it it's 41Nm or just reef down on it with something long like a breaker bar. Re-apply medium loctite to the extractor threads, put a thin layer of grease on any intermediary washer between the crank bolt and extraction cap, and install the extraction cap tightly.