MultiTech rCell Modem Test Error: "Could not establish trust relationship for the SSL/TLS secure channel"

MultiTech rCell Modem Test Error: "Could not establish trust relationship for the SSL/TLS secure channel"

Alert
Newer versions of the rCell modem firmware (5.0 and later) have removed the “enable HTTP” settings available in earlier versions of the firmware. We recommend all users configure the modem for HTTPS access only. 
Known causes of this error:
  1. The modem's SSL certificate has not been installed on the TopView computer. Please consult the MultiTech rCell 100 configuration document for instructions on how to install the SSL certificate.
  2. SSL certificate was installed, but the "Valid From" time is incorrect. (More Information)
Contact TopView Support if you are still receiving this error after installing the modem's SSL certificate.