Twillio and the valid Business URL requirement

How should I best and most directly proceed with successfully complying with the Twilio 'valid Business URL' requirement?

I am attempting to register our company with Twilio by providing our business website URL: http://www.inspire-every-child.org/.  I am being blocked by an error message stating the URL is invalid. Our URL, which has been working for many years, should be 'valid.'

One area of 'Validation' for Twilio that may be a causative factor is certificates. The Twilio documentation on acceptable 'Valid Business URLs' that delves into this point in the area of certificates reads as follows:

SSL Certificate Validation:

• Twilio has implemented additional safeguards around SSL certificate validation. If your URL uses HTTPS, ensure the SSL certificate is valid and issued by a trusted Certificate Authority (CA). Self-signed, expired, or mismatched domain certificates may cause the URL to be rejected.
• For more details, refer to the  Security Update on SSL Certificate Validation.
  
   Security Update on SSL Certificate Validation referred to above reads as follows:
  

  What is the purpose of this safeguard?

  The certificate validation process aims to prevent Man-in-the-Middle attacks on HTTPS connections.
   

  How does this safeguard impact me?

  This change impacts customers who use HTTPS endpoints to receive requests from Twilio. If certificate validation is enabled and you are using a self-signed, expired, mismatched domain or a certificate not issued by a trusted certificate authority*, HTTP requests to your application from Twilio will fail, resulting in an error notification. Error notifications are available in Monitor under Alerts.

  *Twilio considers any Certificate Authority included in the Mozilla Trust Store and Java CA Store to be trusted.