Review and Sign link missing

I have an issue on the recipient side - the link to review and sign doesn't appear in the email.  I viewed the source of the email and this piece of HTML code doesn't show anything:

<!--/*SC*/ CALL TO ACTION /*EC*/-->
<center>
<!--/*SC*/ CALL TO ACTION MSO /*EC*/-->
<!--/*SC*/[if mso]>
<table align="center" width="150" border="0" cellpadding="0" cellspacing="0" style="width:150px;">
<tr>
<td height="28px">
&nbsp;
</td>
</tr>
<tr>
<td height="32" valign="middle" style="background-color:#ffc423; height:32px; padding: 8px 14px; border-radius:20px">
<center>
<a target="_blank" href="https://account.na2.echosign.com/public/esign?tsid=LINK_REMOVED_FOR_PRIVACY" style="background-color:#ffc423; color:#333333; display:inline-block; font-size: 15px; font-weight: 700 !important; line-height:28px; text-decoration:none; -webkit-text-size-adjust:none; padding:8px 14px">
Review and sign
</a>
</center>
</td>
</tr>
<tr>
<td height="28px">
&nbsp;
</td>
</tr>
</table>
<![endif]/*EC*/-->
<!--/*SC*/[if !mso]> <!>
<! END CALL TO ACTION MSO >

<! CALL TO ACTION NON MSO>
<div style="text-align: center; margin: 31px 0;">
<a target="_blank" href="https://account.na2.echosign.com/public/esign?tsid=LINK_REMOVED_FOR_PRIVACY" style="background-color: #ffc423; border-color: #ffc423; color: #333333!important; border-width: 2px; border-style: solid;
border-radius: 20px; display: inline-block; height: auto; min-width: 72px; padding: 8px 14px; font-size: 15px; font-weight: 700 !important;
text-decoration: none; margin: 0; justify-content: center;">
Review and sign
</a>
</div>
<! END CALL TO ACTION NON MSO >
<! <![endif]/*EC*/-->
</center>
<!--/*SC*/ END CALL TO ACTION /*EC*/-->

We use Outlook 2016 but it's still invisible if the email is forwarded to gmail or opened in browser.  If I follow the link from the source I get to the document, but I'd really like to find a way to fix it as we're going to receive a few Adobe Sign emails in the near future.