Yeah, the header didn't have any power, tested it with a voltmeter before returning it. The motherboard is a MSI Z370 Tomahawk, the bios settings allows to control the speed of all fan headers incl the waterpump one but it doesn't allow to power on/off each header, all of them *should* have power for as long as the motherboard is working.
It has 4 headers for case fans, one for cpu, one for the waterpump. every single one of them works fine out of the box but the 4th header didn't get any power. If i unplug the fan that was connected there and connect it to any other header while the mobo is running, the fan works without any issue.
Edit: I could have kept the mobo and use a spliter instead since it didn't bother me a lot anyways but if it has a header broken who knows what other issue it could have