[Error] XMLHttpRequest cannot load https://abc:9443/FlexmonsterProxy/Handshaking due to access control checks.
[Error] Failed to load resource: Preflight response is not successful (Handshaking, line 0)
Please suggest us to resolve this issue.
Note: This issue is only in Safari.
Thank you for posting your question.
We’ve investigated this issue a little bit further and stumbled upon multiple posts on Apple forums back from 2015, where it was mentioned that new mixed content policy was introduced in Safari 9. Due to this policy Safari no longer allows the user to load HTTP content on HTTPS pages, as well as vice versa, while also making it impossible to disable this block.
With that in mind, what we would suggest is to serve all your pages via HTTPS instead of HTTP in order to avoid the mixed content block.
Please let us know if this helps.