Hi,
Have you tried a different known working USB-C charge cable or a compatible charger to see if the speaker started to charge OK?
If it is <12 months old, you should be able to get it replaced under [https://support.jbl.com/us/en/howto/jbl-warranty-information-us|warranty] (click on the country flag in the left top corner of the page to select your location and then search to find what the warranty period is there, for the speaker