Exception thrown when using /userinfo in Azure B2C custom policies

We have set up oAuth2 idp and for customendpoint we use /userinfo endpoint of the openid IDP.

We have tried various things but continue to get the exception - "AADB2C: An exception has occurred" and not much other information even in insights except the below:

We are using the following Technical Profile:

                <TechnicalProfile Id="iddataweb-OIDC-userinfo">
us/answers/questions/2247510/problem-adding-external-identity-provider-with-azu -->
                    <DisplayName>IDW Login</DisplayName>
                    <Protocol Name="OpenIdConnect" />
                    <Metadata>
                        <Item Key="issuer">https://iddatawebb2c.b2clogin.com/your-tenant-id/v2.0/</Item>
                        <Item Key="authorization_endpoint">https://preprod1.iddataweb.com/axn/oauth2/authorize</Item>
                        <Item Key="AccessTokenEndpoint">https://preprod1.iddataweb.com/axn/oauth2/token</Item>
                        <Item Key="ClaimsEndpoint">https://preprod1.iddataweb.com/axn/oauth2/userInfo</Item>

                        <Item Key="client_id">someid</Item>
                        <Item Key="response_types">code</Item>
                        <Item Key="response_mode">query</Item>
                        <Item Key="scope">openid profile</Item>
                        <Item Key="HttpBinding">POST</Item>
                        <Item Key="UsePkce">true</Item>
                        <Item Key="UsePolicyInRedirectUri">false</Item>
                    </Metadata>
                    <CryptographicKeys>
                        <Key Id="client_secret" StorageReferenceId="B2C_1A_secret" />
                    </CryptographicKeys>
                    <OutputClaims>
                        <OutputClaim ClaimTypeReferenceId="issuerUserId" PartnerClaimType="sub" />
                        <OutputClaim ClaimTypeReferenceId="displayName" PartnerClaimType="sub" />
                        <OutputClaim ClaimTypeReferenceId="givenName" PartnerClaimType="sub" />
                        <OutputClaim ClaimTypeReferenceId="surname" PartnerClaimType="sub" />
                        <OutputClaim ClaimTypeReferenceId="identityProvider" DefaultValue="cylogin" />
                        <OutputClaim ClaimTypeReferenceId="authenticationSource" DefaultValue="socialIdpAuthentication" />
                    </OutputClaims>
                    <OutputClaimsTransformations>
                        <OutputClaimsTransformation ReferenceId="CreateRandomUPNUserName" />
                        <OutputClaimsTransformation ReferenceId="CreateUserPrincipalName" />
                        <OutputClaimsTransformation ReferenceId="CreateAlternativeSecurityId" />
                        <OutputClaimsTransformation ReferenceId="CreateSubjectClaimFromAlternativeSecurityId" />
                    </OutputClaimsTransformations>
                    <UseTechnicalProfileForSessionManagement ReferenceId="SM-SocialLogin" />
                </TechnicalProfile>

and user journey as

        <UserJourney Id="SignUpOrSignInWithExternalOAuth2">
            <OrchestrationSteps>
                <!-- Step 1: Check for existing session -->
                <OrchestrationStep Order="1" Type="CombinedSignInAndSignUp" ContentDefinitionReferenceId="api.signuporsignin">
                    <ClaimsProviderSelections>
                        <ClaimsProviderSelection TargetClaimsExchangeId="ExternalOAuth2Exchange" />
                    </ClaimsProviderSelections>
                </OrchestrationStep>

                <!-- Step 2: Show error if IDP selection failed -->
                <!-- <OrchestrationStep Order="2" Type="ClaimsExchange">
                    <Preconditions>
                        <Precondition Type="ClaimsExist" ExecuteActionsIf="true">
                            <Value>objectId</Value>
                            <Action>SkipThisOrchestrationStep</Action>
                        </Precondition>
                    </Preconditions>
                    <ClaimsExchanges>
                        <ClaimsExchange Id="SelfAsserted-Unified" TechnicalProfileReferenceId="SelfAsserted-Unified" />
                    </ClaimsExchanges>
                </OrchestrationStep> -->

                <!-- Step 3: Redirect to external OAuth2 provider -->
                <OrchestrationStep Order="2" Type="ClaimsExchange">
                    <ClaimsExchanges>
                        <ClaimsExchange Id="ExternalOAuth2Exchange" TechnicalProfileReferenceId="iddataweb-OIDC-userinfo" />
                    </ClaimsExchanges>
                </OrchestrationStep>

                <!-- Step 4: Read user attributes from UserInfo endpoint -->
                <OrchestrationStep Order="3" Type="ClaimsExchange">
                    <Preconditions>
                        <Precondition Type="ClaimEquals" ExecuteActionsIf="false">
                            <Value>identityProvider</Value>
                            <Value>externalprovider.com</Value>
                            <Action>SkipThisOrchestrationStep</Action>
                        </Precondition>
                    </Preconditions>
                    <ClaimsExchanges>
                        <ClaimsExchange Id="AADUserReadWithObjectId" TechnicalProfileReferenceId="AAD-UserReadUsingObjectId" />
                    </ClaimsExchanges>
                </OrchestrationStep>

                <!-- Step 5: Create or update local account -->
                <OrchestrationStep Order="4" Type="ClaimsExchange">
                    <ClaimsExchanges>
                        <ClaimsExchange Id="AADUserWrite" TechnicalProfileReferenceId="AAD-UserWriteUsingAlternativeSecurityId" />
                    </ClaimsExchanges>
                </OrchestrationStep>

                <!-- Step 6: Enrich claims if needed -->
                <!-- <OrchestrationStep Order="5" Type="ClaimsExchange">
                    <ClaimsExchanges>
                        <ClaimsExchange Id="EnrichClaims" TechnicalProfileReferenceId="EnrichClaimsFromUserInfo" />
                    </ClaimsExchanges>
                </OrchestrationStep> -->

                <!-- Step 7: Issue tokens -->
                <OrchestrationStep Order="5" Type="SendClaims" CpimIssuerTechnicalProfileReferenceId="JwtIssuer" />

            </OrchestrationSteps>
            <ClientDefinition ReferenceId="DefaultWeb" />
        </UserJourney>

Any help would be appreciated