In a Prisma Access mobile user deployment using SAML through the Cloud Identity Engine, the Cloud Identity Engine — not Strata Cloud Manager directly — is the SAML service provider entity that actually exchanges metadata and assertions with the customer ' s IdP; Strata Cloud Manager ' s role is to reference the authentication profile the Cloud Identity Engine has already established, not to independently hold the SAML relationship with the IdP. The error message explicitly names " CIE-SAML " as the point of failure, which is a strong, direct indicator that the misconfiguration lives in the metadata exchange between the Cloud Identity Engine and the IdP specifically, rather than anywhere downstream in Strata Cloud Manager itself. A 400 Bad Request returned to the portal after IdP authentication typically points to a malformed or mismatched SAML assertion, entity ID, or ACS URL between these two specific parties, making a targeted review of CIE-to-IdP metadata (option C) the correct, root-cause-focused action, since the question also states that " URLs and certificates are correctly configured " from the general check already performed in option A ' s framing — pointing the investigation toward CIE specifically. Reviewing Security policy rules (option B) addresses network-layer reachability, not SAML protocol-level metadata errors, and would not explain a 400 Bad Request occurring after successful IdP login. Reviewing Authentication logs (option D) is a reasonable general diagnostic step but does not, by itself, identify the root cause the way directly verifying the CIE-to-IdP metadata configuration does.