Hello
By default the Joomla Media Manager does not allow for SVG. You could try adding your SVG logo to the template manually by editing the following line in your templates header.php (../templates/[YourTemplate]/php/layouts/header.php - line 8)...
<img class="logo-image" src="/<?php echo $this->baseurl ?>/<?php echo $logoimagefile; ?>" alt="Logo" />
Replacing with something this (edit to taste)...
<img class="logo-image" src="/<?php echo $this->baseurl ?>/images/yourlogo.svg" alt="Logo" />
Ciarán