I've now had four USB rechargeable front bike lights fail due to the USB port. I plug in the USB micro cable and nothing happens. On one new Niterider light it worked only for a few days. On another, it was months before failure to charge. The youth at my local bike shop said "we see this" but had nothing else useful to add. The lights get plugged into a powered Anker USB hub. Any insight into this problem would be greatly appreciated.
This really needs more investigation on your part to come up with the answer. Start eliminating possibilities and see if the symptom stays or moves away. Iterate on this and figure out the root cause.
Do you ride in the rain a lot ? Water may be damaging the port, preventing charging. Try charging one of those older lights again. They may have had time to "dry out" inside.
Do you have another cable to try? USB cables do wear out, they get sloppy with too many insert cycles.
Do you have access to a USB power meter to measure the current draw?
Have you tried opening a "dead" light to see if the batteries inside have any charge? Also look for corrosion while you're in there.
Can you try charging one directly from your computer or from a USB wall charger? A hub might not have enough power to charge the light and run other attached items.
Even if other USB devices charge fine on this cable/hub combo, your light may draw more current than it can give.
Micro-USB connectors break rather easily if you attempt to pair them "upside down". Memorize the needed orientation of the charging cable. A partially broken socket may work with some connectors only, and not with others.
These connectors are difficult to solder by hand, while some say they can do. If you short circuit the low end lithium battery without internal fuses, various nasty things may happen. The battery normally has the own connector inside the lamp, disconnect it before doing anything else. Start testing from charging the flat battery. From the other side, there are places on a bicycle where you need to known even more what are you doing.
Only the two outer pins are normally required for charging (+5 V and ground) and you may be able to find the easier tap points on the printed circuit board. In my case the connector was ripped out with all PCB tracks but ground and +5V buses going from it were wide and I found suitable alternative connecting points. I placed Molex SL instead of USB, it mostly fits into place and can be covered by the same cap. The setup as mine has open pins but it should only be 5V there and I connect this part before I connect cable to the charger. Maybe some closed connector could be more recommended but I did not find any small enough.