From experience (and I mean I have spent weeks figuring out why some PoE cables don't work and others do) I can say this: Ensure that your use RJ45 type B wiring and not type A for PoE. In some cases I have not been able to get type A to work. The power is transmitted, the powered device comes on, but there's no communication with the device, not even on layer2 (powered device MAC address is not visible on the switch).
So, use type B.
On a short cable (a few meters) it makes no difference, but on 70m+ it does. Using CAT5/5e or CAT6/6a cable, both cause problems on type A but not type B.
Although this is not strictly a wiring issue, to further explain the problems that can be experienced with CAT6 cable over long length (50m+), eejim writes at https://community.ubnt.com/t5/UniFi-Wireless/Unexpected-PoE-Cable-length-limitations-with-UniFi-Switch-16/m-p/1918103/highlight/true#M226319:
"CAT6/6A cables are being made with 26 gauge cable.
The biggest problem with 10Gb ethernet is crosstalk between the wires/pairs in the cable. There's just one way to lessen this - move the wires physically farther apart. One way the cable manufacturers have found to accomplish this while not making the cable too large - there is actually a spec for the maximum diameter of ethernet cable - is to make the copper wire itself smaller, so the insulation is thicker, so there's more space between conductors. This actually works (and they love it because there's less copper which saves them money, but they can charge more for the cable because, well, it's spec'd higher, right?) , but it causes the problem you are seeing - the smaller conductor has higher resistance and therefore more voltage drop than the standard CAT5e 24 gauge wire. So with longer CAT6 cables the PoE limitation needs to be accounted for. This is why I never use Cat6/6A cables except for very specific things, and never ever for PoE.
Change out your cable to CAT5e and the problems will go away. And at gigabit speeds it will work just fine up to 100 meters, even at 24V PoE."
Having taken note of eejim's comments, I have checked with suppliers and there is a better quality CAT6/CAT6A available that uses 23 gauge wire, which will not suffer from these issues when used for POE purposes.