nginx-proxy-manager/frontend/js/app/error/main.ejs

<i class="fe fe-alert-triangle mr-2" aria-hidden="true"></i>
<%= code ? '<strong>' + code + '</strong> &mdash; ' : '' %>
<%- message %>

<% if (retry) { %>
    <br><br><a href="#" class="btn btn-sm btn-warning retry"><%- i18n('str', 'try-again') %></a>
<% } %>