Hey Bo,
first of all I would recommend using our Child Themes templates to prevent any errors on your side. So on the left side of the member area you can find the “Child Themes” section where you can download the child themes. Other than that page sure that your page template is defined meaning that on the top of the file you’ve added:
< ?php
/* Template Name: Custom Template */
?>
or something similar.
Also make sure to clear your cache.