None has worked for me. But his one did.
Since the Bootstrap 4 .row class is now display:flex you can simply use the new align-self-center flexbox utility on any column to vertically center it:
<div class="row">
<div class="col-6 align-self-center">
<div class="card card-block">
Center
</div>
</div>
<div class="col-6">
<div class="card card-inverse card-danger">
Taller
</div>
</div>
</div>
I learned about it from https://medium.com/wdstack/bootstrap-4-vertical-center-1211448a2eff