1 strand not working

I have one of my four strands that is now not working.  It originally worked perfectly fine, until I disconnected it from the other strands, but now it is not working properly 

Dear user,

We sincerely apologize for any inconvenience this issue may have caused. 
We have sent you a direct message to provide further assistance.
We look forward to your response to that message.

Best regards,
Lepro Customer Service Team