SAP B1 external web access - HTTP 500 ERROR

Hi all, I have configured the web access of SAP B1 9.2, and it is working correctly inside the LAN, but from the external networking using the public IP, shows the next error message:

java.lang.NullPointerException: while trying to invoke the method com.sap.security.saml2.cfg.metadata.SAML2MetadataTrustedIdP.getSingleSignOnEndpoints() of a null object loaded from local variable 'provider'
	com.sap.businessone.saml2.sp.EndPointUtils.getURLFromIDPMetadata(EndPointUtils.java:106)
	com.sap.businessone.saml2.sp.SAML2SPSession.setIDPMetadata(SAML2SPSession.java:353)
	com.sap.businessone.saml2.sp.SAML2SPSession.configIDPExtMetadata(SAML2SPSession.java:379)
	com.sap.businessone.saml2.sp.SAML2SPSession.createIDPMetadataInstance(SAML2SPSession.java:236)
	com.sap.businessone.saml2.sp.SAML2SPSession.<init>(SAML2SPSession.java:89)
	com.sap.businessone.saml2.sp.filters.LoginRequiredFilter.doFilter(LoginRequiredFilter.java:259)
	com.sap.b1.sld.common.web.filter.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:49)
	com.sap.b1.sld.httpDispatcher.b1WebServer.HelpApplicationFilter.doFilter(HelpApplicationFilter.java:55)

Does someone has the same experience?.

In SLD - Excternal Address Mapping is correctly configured, at least I think so because in other implementation I could access from the external network with the same configurations.