Front end form with Matrix won't add more than one row I have Notification entry with sendTo field and nViewed matrix:
- viewedBy = Users field, limit of 1
- viewedDateTime = Plain Text

User's don't see whole front end form, just a 'Mark as Read' link. The link uses js to populate viewedDateTime and submit form. My form:

&lt;form id="update-{{ msg.id }}" method="post" accept-charset="UTF-8"&gt;
   {{ csrfInput() }}
   &lt;input type="hidden" name="action" value="entries/save-entry" /&gt;
   &lt;input type="hidden" name="redirect" value="{{ theredirect }}" /&gt;
   &lt;input type="hidden" name="sectionId" value="{{ msg.section.id }}" /&gt;
   &lt;input type="hidden" name="entryId" value="{{ msg.id }}" /&gt;
   &lt;input type="hidden" name="fields[nViewed]" /&gt;
   &lt;input type="hidden" name="fields[nViewed][new1][type]" value="viewed" /&gt;
   &lt;input type="hidden" name="fields[nViewed][new1][enabled]" value="1" /&gt;
   &lt;input type="hidden" name="fields[nViewed][new1][fields][viewedBy][]" value="{{ currentUser.id }}" /&gt;
   &lt;input type="hidden" name="fields[nViewed][new1][fields][viewedDateTime]" value="" /&gt;
   &lt;button type="submit" class="tx-11 btn bd-0"&gt;Mark as read&lt;/button&gt;
&lt;/form&gt;


When the first user from sentTo clicks the 'Mark as Read' link, they get added to the matrix. All good.

When the second user from sentTo (testing on a different browser) clicks the 'Mark as Read' link it overwrites the first users row instead of adding another row to matrix.

I've also tried using field name="fields[nViewed][new{{ currentUser.id }}]... to make them unique but still overwrites.

What am I missing?
Amanda
According to the craft cms docs


  To show a “New Block” form, first come up with a temporary ID for the
  block, prefixed with new:. For example, new:1, new:2, etc.


so, you need to you use prefix new: with the colon is a must.