As "caixinhas" ficaram embaixo

Era para ficar uma ao lado da outra, mas ficaram embaixo. Onde será que está o problema?

.panel-speakers{
    padding-top: 40px;
    background: #EF7247;

}

.panel-speakers .about-speakers{
    text-align: center;
}

.panel-speakers .title{
    color: white;
    font-size: 40px;
    margin-bottom: 16px;
}

.panel-speakers .subtitle{
    color: white;
    font-size: 32px;
    margin-bottom: 16px;
}

.panel-speakers .speaker{
    text-align: center;
}

.panel-speakers .speaker{
    background: white;
    display: inline-block;
    margin: 0 16px 32px 0;
    padding: 18px;
    border-radius: 10px;
    width: 250px;
    vertical-align: top;
}

.panel-speakers .speaker-image{
    border-radius: 50%;
}

.panel-speakers .speaker-name{
    margin-top: 10px;
}

.panel-speakers .speaker-bio{
    font-weight: bold;
    margin-top: 16px;
}

.panel-speakers .speaker-speach{
    margin-top:16px;