using nested flexbox but media query cant seem to work, help please

Watched the code and your problem on flex-direction: column; in your master branch you didn't change the value:

.flexbox {
  height: 100vh;
  width: 100vw;
  max-width: 1440px;
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: row;
  flex: 1 2 1080px;
  margin: auto;
}

@media screen and (max-width: 375px) {
  .flexbox {
    flex-direction: row; // this value need to be column
  }
}