What is causing this Error?

The Bridge is unable to establish communication to the UTG via the assigned SSL\TLS secure channel certificate.

Example:

Attempting a Token Exchange before establishing an SSL\TLS certificate in the UTG API interface settings.

How do I resolve this Error?

You need to generate a new SSL\TLS certificate for use with the Shift4 Bridge and UTG to communicate and allow the token exchange. 

Refer to the Using the Shift4 Certificate Generator article for more information.