Still no token.

It was just the same as the one that came with the add-on. I also tried Patricia's suggestion but no luck.

<perch:form id="profile" method="post" app="perch_members">

    <div>
        <perch:label for="first_name">First name</perch:label>
        <perch:input type="text" id="first_name" required="true" label="First name" />
        <perch:error for="first_name" type="required">Please add a your name</perch:error>
    </div>

    <div>
        <perch:label for="last_name">Last name</perch:label>
        <perch:input type="text" id="last_name" required="true" label="Last name" />
        <perch:error for="last_name" type="required">Please add a your name</perch:error>
    </div>

    <div>
        <perch:label for="email">Email</perch:label>
        <perch:input type="email" id="email" required="true" placeholder="you@company.com" />
        <perch:error for="email" type="required">Please add a your email address</perch:error>
        <perch:error for="email" type="format">Please check a your email address</perch:error>
    </div>

    <div>
        <perch:input type="submit" value="Save" />
        <input id="token" name="token" value="<perch:members id="token" />" type="hidden">
    </div>

    <perch:success>
        <p>Your details have been updated.</p>
    </perch:success>

</perch:form>

That worked! Thanks again, Robert!

Cool...