I've read something in the net about similar problems and find out, that it could be a rewrite problem. In the root directory from osTicket is a file web.config within some rewrite rules:
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<directoryBrowse enabled="false" />
<rewrite>
<rules>
<rule name="HTTP api" stopProcessing="true">
<match url="^(.*/)?api/(.*)$" ignoreCase="true"/>
<conditions>
<add input="{REQUEST_FILENAME}" matchType="IsFile"
ignoreCase="false" negate="true" />
<add input="{REQUEST_FILENAME}" matchType="IsDirectory"
ignoreCase="false" negate="true" />
</conditions>
<action type="Rewrite" url="{R:1}api/http.php/{R:2}"/>
</rule>
<rule name="Site pages" stopProcessing="true">
<match url="^(.*/)?pages/(.*)$" ignoreCase="true"/>
<conditions>
<add input="{REQUEST_FILENAME}" matchType="IsFile"
ignoreCase="false" negate="true" />
<add input="{REQUEST_FILENAME}" matchType="IsDirectory"
ignoreCase="false" negate="true" />
</conditions>
<action type="Rewrite" url="{R:1}pages/index.php/{R:2}"/>
</rule>
<rule name="Staff applications" stopProcessing="true">
<match url="^(.*/)?scp/apps/(.*)$" ignoreCase="true"/>
<conditions>
<add input="{REQUEST_FILENAME}" matchType="IsFile"
ignoreCase="false" negate="true" />
<add input="{REQUEST_FILENAME}" matchType="IsDirectory"
ignoreCase="false" negate="true" />
</conditions>
<action type="Rewrite" url="{R:1}scp/apps/dispatcher.php/{R:2}"/>
</rule>
</rules>
</rewrite>
<defaultDocument>
<files>
<remove value="index.php" />
<add value="index.php" />
</files>
</defaultDocument>
</system.webServer>
</configuration>
But I don't know if it is important for my problem and I also don't know, how I can convert this rules into URLToolkit