Cannot add Read-Only QuickBooks Web Connector app

I am trying to create a web app that can communicate with QuickBooks Desktop.

I have set up a SOAP server, but when I click "Add an Application" in the Web Connector and select my QWC file it gives:

StatusCode=3263. Status message: This request cannot be completed because the integrated application had requested read-only access.  Have the integrated application request read/write access, and have the QuickBooks administrator grant this access.

When I change the <IsReadOnly>true</IsReadOnly> to <IsReadOnly>false</IsReadOnly>, the app is added fine. Any ideas on why this might be happening? I haven't been able to find anyone doing a read-only SOAP server, so I don't really have any examples to go off of. Is there a different way I need to configure it?

My QWC File:

<?xml version="1.0"?>
<QBWCXML>
    <AppName>My App Name</AppName>
    <AppID></AppID>
    <AppURL>https://mywebsite.com/path-to-web-connector-soap-server</AppURL>
    <AppDescription></AppDescription>
    <AppSupport>https://mywebsite.com/support</AppSupport>
    <UserName>quickbooks</UserName>
    <OwnerID>{2e081sd3-2fe5-4de5-8s6a-e70ss35ss0d8}</OwnerID>
    <FileID>{14C3sC64-0sC0-4ssD-BFs4-151s95B0729C}</FileID>
    <QBType>QBFS</QBType>
    <Scheduler>
        <RunEveryNMinutes>2</RunEveryNMinutes>
    </Scheduler>
    <IsReadOnly>true</IsReadOnly>
</QBWCXML>

My SOAP Server:

<?php
require_once '../QuickBooks.php';

if (function_exists('date_default_timezone_set')) {
    date_default_timezone_set('America/New_York');
}
$user = 'quickbooks';
$pass = 'password';
$map = array(
    QUICKBOOKS_QUERY => array('_request_xml_query', '_response'),
);
$errmap = array();
$hooks = array();
$log_level = QUICKBOOKS_LOG_DEVELOP;
$soapserver = QUICKBOOKS_SOAPSERVER_BUILTIN;
$soap_options = array();
$handler_options = array(
    'deny_concurrent_logins' => false,
    'deny_reallyfast_logins' => false,
);
$driver_options = array();
$callback_options = array();
$dsn = 'mysqli://usr:DBPassword@localhost/db_name';
if (!QuickBooks_Utilities::initialized($dsn)) {
    QuickBooks_Utilities::initialize($dsn);
    QuickBooks_Utilities::createUser($dsn, $user, $pass);
} else {
    $Server = new QuickBooks_WebConnector_Server($dsn, $map, $errmap, $hooks, $log_level, $soapserver, QUICKBOOKS_WSDL, $soap_options, $handler_options, $driver_options, $callback_options);
    $response = (string) $Server->handle(true, true);
}

function _request_xml_query($requestID, $user, $action, $ID, $extra, &$err, $last_action_time, $last_actionident_time, $xml, $idents)
{
    return str_replace('{REQUEST_ID}', $requestID, $extra);
}

function _response($requestID, $user, $action, $ID, $extra, &$err, $last_action_time, $last_actionident_time, $xml, $idents)
{
    saveResponse($xml);
}

function saveResponse($xml) {
    ...
}