We are using AD B2C custom policies for our sign-in flows and we are also doing language customization.
Even if it's possible to localize the error messages using custom policies (https://learn.microsoft.com/en-us/azure/active-directory-b2c/localization-string-ids), for example:
<LocalizedResources Id="api.localaccountsignup.en">
<LocalizedStrings>
<LocalizedString ElementType="ErrorMessage" StringId="DefaultUserMessageIfRequestFailed">Failed to establish connection to restful service end point.</LocalizedString>
<LocalizedString ElementType="ErrorMessage" StringId="UserMessageIfCircuitOpen">Unable to connect to the restful service end point.</LocalizedString>
<LocalizedString ElementType="ErrorMessage" StringId="UserMessageIfDnsResolutionFailed">Failed to resolve the hostname of the restful service endpoint.</LocalizedString>
<LocalizedString ElementType="ErrorMessage" StringId="UserMessageIfRequestTimeout">Failed to establish connection to restful service end point within timeout limit.</LocalizedString>
</LocalizedStrings>
</LocalizedResources>
I cannot find a key for the message "Unable to validate the information provided."
Also, it doesn't have an ID.