MM,
Polarity is correct, checked it with a voltage meter. I have had this with other cells and it was the balancer connection.
I have another charger and will try it. Glad to hear others have had this problem if we solve it maybe it will help others. Thinking about it, might be the balancer block or its connection into the charger.
Best, DennisT
UPDATE: I tried changing the balancer block from my old TP610 and it still gave the same error. I just tried using the old TP610 from the power supply and its charging just fine. I will contact Thunder Power and see what they say and post back what I find out.