I’d advise to contact support just in case, perhaps there’s a warranty case … https://support.fairphone.com/hc/en-us.
Else … If you need a workaround to charge the battery, there are universal external battery chargers, in case of need I have this one for the Fairphone 3 battery (I just fetched some links to where it’s available currently, it might be available elsewhere, too, there’s a version with an LED indicator and a version with an LCD display) …
https://www.ebay.de/itm/401760527578
https://www.amazon.de/dp/B010PUJ5W8
https://www.amazon.de/dp/B00UYUZ1L4
If you want to look up other chargers … The charging contacts have to be thin enough for the Fairphone 3 battery contacts, this is not a given with all universal chargers.