Login information not displayed in 1Password

I've just saved a new login manually in Safari (13.0.5) but when I open the 1Password app (7.4.3) most of the information is not displayed.
The login screen consists of a "username" field (it's not labelled in that way but effectively that is what it is) and 4 fields for date of birth 3 of which are dropdown lists (Japanese era, year, month, day).
When I open 1Password the only information which displays in the login is the URL and a username (but the username displayed is actually the year which is the single text field from the date of birth section of the form).

Using "open and fill" works so all the information is saved somewhere, it just doesn't display so it's not a critical problem. Is there any way of making it show the information which it correctly puts into the form?

The site is "https://www2.i-helios-net.com/pc/hw2_pc_login.php?MID=" with 4 figures after the "=" which is effectively reveals personal information so I'm not posting that. In case that makes it impossible to see what the problem is, the html of the login form is below. I've replaced personal information with "ManuallyRedactedInfo". Sorry about the poor layout.

<form name="formpost" action="https://www2.i-helios-net.com/pc/hw2_pc_index00.php" method="post">
<input type="hidden" name="MID" value="ManuallyRedactedInfo">Shadow Content (User Agent)</input>
<p class="indent50">
</p><table class="login">
<tbody><tr><th>診察券番号</th><td><input type="txt" name="login_id" size="20" maxlength="15" style="ime-mode: disabled;" value="" data-com.agilebits.onepassword.initial-value="" class="">Shadow Content (User Agent)<div contenteditable="plaintext-only">ManuallyRedactedInfo</div></td></tr>
<tr><th>生年月日</th><td><select name="reki">
<option value="1">西暦</option>
<option value="2">明治</option>
<option value="3">大正</option>
<option value="4">昭和</option>
<option value="5">平成</option>
<option value="6">令和</option>
</select>   
<input type="text" name="year" size="4" maxlength="4" style="ime-mode: disabled;" value="" data-com.agilebits.onepassword.initial-value="" class="">Shadow Content (User Agent)<div contenteditable="plaintext-only">ManuallyRedactedInfo</div>年
<select name="month">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
<option value="6">6</option>
<option value="7">7</option>
<option value="8">8</option>
<option value="9">9</option>
<option value="10">10</option>
<option value="11">11</option>
<option value="12">12</option>
</select>
月
<select name="day">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
<option value="6">6</option>
<option value="7">7</option>
<option value="8">8</option>
<option value="9">9</option>
<option value="10">10</option>
<option value="11">11</option>
<option value="12">12</option>
<option value="13">13</option>
<option value="14">14</option>
<option value="15">15</option>
<option value="16">16</option>
<option value="17">17</option>
<option value="18">18</option>
<option value="19">19</option>
<option value="20">20</option>
<option value="21">21</option>
<option value="22">22</option>
<option value="23">23</option>
<option value="24">24</option>
<option value="25">25</option>
<option value="26">26</option>
<option value="27">27</option>
<option value="28">28</option>
<option value="29">29</option>
<option value="30">30</option>
<option value="31">31</option>
</select>
日
</td></tr>
</tbody></table>
<p></p>
<br>
<center>
<p><input type="button" name="btnOK" value="ログイン" onclick="javascript:fncSubmit(&quot;診察券番号&quot;);return false" style="cursor:pointer">　<input type="button" name="btnReset" value="リセット" onclick="javascript:fncReset();return false" style="cursor:pointer">
</p>
</center>
</form>

1Password Version: 7.4.3
Extension Version: Not Provided
OS Version: MacOS 10.14.6
Sync Type: Not Provided