Hi, YuYu,
You use TWR-56F8200 and Multilink Universal device to download code, in the case, you have to do as the following procedures:
1)Open J20 jumper
2)open all jumper on J21
Pls have a try.
xiangjun_rong_0-1627872331769.png
Hope it can help you
BR
XiangJun Rong