3641821 - "Error loading trusted provider data" in SAML2

When accessing transaction SAML2 > Trusted Providers tab and/or when trying to add a new IdP through metadata file, below message appears:
"Error loading trusted provider data. You can get more information by collecting traces using tool http(s)://host:port/sap/bc/webdynpro/sap/sec_diag_tool?sap-client=XXX"

And

A SAML2 trace collected via Sec_diag_tool contains the following message:
"SAML20 SP (client <client_number> ): |Error occurred: {Parameter IF_ENTITY_TYPE was either incorrectly set or not set in method CL_SAML20_ENTITY=>GET_ENTITY. }|"

• SAP NetWeaver
• ABAP platform

Parameter IF_ENTITY_TYPE was either incorrectly set or not set in method CL_SAML20_ENTITY=>GET_ENTITY, Error loading trusted provider data, SAML2, SAML_ENTITY, SAML_ENTITY_E, SAML20 CX_SAML20_CORE: No entity in with KEY <key number> in client <client number> found, No entity in with KEY, In client &MANDT& no trusted entity for <SID> was found, In client &MANDT& no trusted entity , KBA , BC-SEC-LGN-SML , SAML 2.0 for ABAP , Problem