If I understand your question correctly, is your question:
A. No response to emails or queries
There is no response to your emails or query about the employment of a candidate previously working with them but currently working with your organization.
B. Employer is untraceable or shut down
The employer is untraceable or shut down, so you are unable to get in touch with them.
For both cases, I suggest getting back to your candidate and asking them to submit email IDs, telephone numbers, or contact details of their previous managers, colleagues, clients, or vendors.
Brightlist Global
www.brightlistglobal.com
[Phone Number Removed For Privacy-Reasons]