在div上设置。

HTML:

        <div class="flex-item">
            <img src="img/Nike.png" alt="Nike" class="img-responsive"/>
            <p>Nike.com</p>
        </div>

CSS:

       .flex-item{
         display:flex;
        }

我试过这样。它起作用了。

<div class="surfooter">
  <div class="flex-container">
      <div class="flex-item">
          <img src="img/Nike.png" alt="Nike" class="img-responsive"/>
          <p>Nike.com</p>
      </div>
      <div class="flex-item">
          <img src="img/Adidas.png" alt="Adidas" class="img-responsive" />
          <p>Adidas.com</p>
      </div>
  </div>
</div>

CSS

.surfooter{
  padding-bottom: 50px;
  padding-top: 50px;
  background-color: #466964;
  color: white;
  font-size: 16px;
  position: relative;
}

.flex-container {
  display: flex;
  flex-flow: row wrap;
  justify-content: space-between;
  height: 200px;
  position: relative;
}

.flex-item {
  margin: auto;
  width: auto;
  height: auto;
  display: flex;
  justify-content: center;
  align-items: center;
}

.flex-item p{
  color: white;
  font-size: 1.41em;
  font-weight: bold;
  line-height: 1.3em;
  width: 80%;
  margin: 0 auto;
}

.flex-item img{
  object-fit: cover;
  border-radius: 100%;
  
}

将您的类更改为这个，希望这样可以解决您的问题。

null

.flex-item {
   display:flex;
   flex-direction:row;
  }