When trying to sign in to access a secured ArcGIS Server feature service on ArcGIS Collector, the following error may be returned:
Error: "java.security.cert.CertPathValidatorException: Trust anchor for certification path not found"
When working with ArcGIS Collector, there is the flexibility to work with secured services from ArcGIS Enterprise deployments. The secured feature services can be added to ArcGIS Online with the option to 'Store credentials' checked, or configured to prompt for credentials when opened on the mobile device.
When working with secured layers added as operational layers without storing credentials, ArcGIS Collector displays a warning, 'Secured layers. You need to sign in to access some of the layers in this map.'
Clicking 'View', opens the Layer List, where the Layer name is marked with a triangular warning sign, 'Sign in required'. Normally, a prompt to enter a username and password to authenticate access to the layer is displayed. However in some cases, the option may not be present.
ArcGIS Collector (iOS) does not return any error, however, ArcGIS Collector (Android) displays the error, 'java.security.cert.CertPathValidatorException: Trust anchor for certification path not found'.
The underlying issue is the SSL Settings on the Web Adaptor configured with the ArcGIS Server site. This setting can be enabled on Internet Information Services (IIS) Manager to require the client to be identified before gaining access to any resource.