DIAGNOSIS Debris (lint, pocket sand) is compacted in the port, or the port's internal solder joints have weakened from strain.
FIX Power off the speaker. Use a plastic (not metal) toothpick or SIM-eject tool to very gently scrape along the bottom of the USB-C port to remove packed lint. Shine a light to inspect.
IF THAT DIDN'T WORK Try multiple, high-quality USB-C cables. If one works and others don't, the port is likely damaged and requires professional repair—the Charge 5 is not designed for user port replacement.
HEADS UP Never force a cable or use the port while the speaker is wet. The port is only for charging/powering other devices; it does not support audio input.