The following Ember Handlebars template renders the 1st row, but does not render the one inside the nested each (or inner each)
<table width="50%">
{{#each someData.items as |item|}}
<tr> <!-- This one RENDERS -->
<td width="25%"><span class="boldTxt">{{item.fld1}}</span></td>
<td width="25%">{{item.fld2}}</td>
</tr>
{{#each item.Reasons as |reason|}}
<tr> <!-- This one does not RENDER -->
<td>{{reason}}</td>
</tr>
{{/each}}
{{/each}}
</table>
You can use each-in to get access to the key (and value):
{{#each-in reasons as |key value|}}
<tr>
<td>{{key}}</td>
</tr>
{{/each-in}}
That said, it’s not great practice IMO to use keys to store data which is what you are doing, a key should be the name of the data not the data itself.
It would be better to either store the reasons as an array of strings (if you only need their names) or an array of objects if you need to store additional data for each reason.