There many reasons for 403 error, you can try to add below code in your web.config file:
<system.webServer>
<httpProtocol>
<customHeaders>
<add name="Access-Control-Allow-Origin" value="*" />
<add name="Access-Control-Allow-Methods" value="GET,PUT,POST,DELETE,OPTIONS" />
<add name="Access-Control-Allow-Headers" value="Content-Type" />
</customHeaders>
</httpProtocol>
</system.webServer>
and you can also try enabled anonymous authentication in iis authentication.
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