I finally figured out why the Special Instructions field isn't displaying as expected...
The Special Instructions box only appears under the shipping address if "Shipping address different than billing?" is selected. If left unchecked, there is no way to enter Special Instructions!
This will be confusing to users who enter their address and don't check the box. I must have have special instructions because of this bug causing us to ask customers to enter shirt sizes upon checkout.
So...How can I get the Instructions box to appear under the default address if users do not select the Different Address box?
This is the workaround I did for now:
To display the Shipping Address info, and Special Instructions field, upon checkout. I made the Different Address checked by default.
Add checked="checked" to:
<label class="mp_form_label"><input type="checkbox" class="mp_form_checkbox" name="enable_shipping_address" value="1" autocomplete="off" checked="checked" ' . checked( true, $enable_shipping_address, false ) . '> <span>' . __( 'Shipping address different than billing?', 'mp' ) . '</span></label>
But I hate hacking core files, and will surely forget this edit upon some future upgrade.
Please advise how I can show the Special Instructions field by default to all customers upon checkout if I am just missing some setting somewhere.
Otherwise, please pass this on to the awesome developers to consider addressing in a future update.