1) Please find other phones, tablets, or computers that support video output to test whether have the same issue or not;
2) Please check whether your monitor has a VGA interface, and whether you use HDMI to VGA cable to connect the hub and monitor. If yes, please use HDMI to HDMI cable.
3) If the same problem still occurs when test with other devices, we can help you apply for a replacement to try.
If the other device tests fine, please check your computer software driver. Such as upgrading bios driver or graphics card driver.(Please contact us)