Here is what you can read in the latest version of Chrome's Dev Tools console when submitting a request to your API:
The SSL certificate used to load resources from https://api.companieshouse.gov.uk will be distrusted in M70. Once distrusted, users will be prevented from loading these resources. See https://g.co/chrome/symantecpkicerts for more information.
Not sure if you were aware, so I guess you'd like to know.
Thanks for the information, we have new certificated to be applied that will resolve this issue.