if its not getting off at 400 degrees its not solder its some form of enamal you will have to scrape off.
It’s solder, the problem is setting the iron to 400 degrees doesn’t mean the solder will be heated to the same. I didn’t dig too deep into mine but it seemed to heatsink hardcore so it wouldn’t get hot enough to reflow. I think a solder gun would probably do the trick but I didn’t have access to one at the time and it took two pencil soldering irons to input enough heat.
definatly feels like solder though
sigh i got my package today from wowgo and it contained 2 charge ports instead of the 1 charge port and a replacement power switch haha. ah well i appreciate them for the gesture and willing to help even thoug hits clearly out of warranty. the pwoer switch doesnt turn off but it has an auto shut off timer on it so i dont mind and recently it started workign again so not sure whats up. but at least i cna charge my board safely now jsut gota install it. but i might leave that for the weekend for when i need to do grocery shopping