I'm having a terribly difficult time getting ANY button to work properly in Gmail... I assume it's something simple I'm missing. Please help!

<!-- BULLETPROOF BUTTON -->
          <tr>
            <td bgcolor="#ffffff" align="left">
              <table width="100%" border="0" cellspacing="0" cellpadding="0">
                <tr>
                  <td bgcolor="#ffffff" align="center" style="padding: 10px 30px 60px 30px;">
                    <table border="0" cellspacing="0" cellpadding="0">
                      <tr>
                          <td align="center" style="border-radius: 5px;" bgcolor="#00AF87" mc:edit="cta button"><a href="https://formatically.com" target="_blank" style="font-size: 16px; font-family: lato; Helvetica, Arial, sans-serif; color: #ffffff; text-decoration: none; color: #ffffff; text-decoration: none; border-radius: 5px; border-top: 17px solid #00AF87; border-right: 40px solid #00AF87; border-bottom: 16px solid #00AF87; border-left: 40px solid #00AF87; display: inline-block;">Confirm Your Account</a></td>
                      </tr>
                    </table>
                  </td>
                </tr>
              </table>
            </td>
          </tr>