With current browsers (tested on Chrome 68.0.3440.106 and FireFox 61.0.1), Sahi is not able to establish connections to HSTS enabled sites due to its self-signed certificates.
Earlier versions allowed to import these certificates nonetheless, but with latest browsers, this option is no longer available and connections can't be established.
See for example:
The owner of github.com has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website.
This site uses HTTP Strict Transport Security (HSTS) to specify that Firefox may only connect to it securely. As a result, it is not possible to add an exception for this certificate.
With current browsers (tested on Chrome 68.0.3440.106 and FireFox 61.0.1), Sahi is not able to establish connections to HSTS enabled sites due to its self-signed certificates. Earlier versions allowed to import these certificates nonetheless, but with latest browsers, this option is no longer available and connections can't be established.
See for example: