Unable to charge the wireless headset (WF-1000X / WF-SP700N).

Check the following.

• The headset may not be fully inserted in the charging case. Insert the headset until they click and make sure that the units are locked in the charging case.
  When charging begins, the red indicators on the headset light on.
  WF-1000X
   
  WF-SP700N
  
• The rechargeable battery in the charging case may have no remaining charge. Charge the charging case.
  The indicator lights up in red while charging the charging case.
  WF-1000X
  
  
  WF-SP700N
  
  
   
• The terminal may be dirty. It is recommended that you clean the terminals on the headset and charging case periodically with a soft dry cloth.
  
  NOTE:
• • If the charging case is charged fully, you can charge the headset for about 2 times.
  • The following situations mean that the rechargeable battery in the charging case has a low remaining charge and the headset cannot be charged.
  • • When the headset is set to the charging case, the red indicator on the headset flashes and then immediately lights off, and the headset powers off.
    • Even when the headset is set in the charging case, the red indicator does not light on or flash, and the headset does not power off.

For more information of how to charge your headset, check the link below.
WF-1000X: https://helpguide.sony.net/mdr/wf1000x/v1/en/contents/TP0001553058.html?search=charge
WF-SP700N: https://helpguide.sony.net/mdr/wfsp700n/v1/en/contents/TP0001613445.html?search=charge