I have the same problem (C++, R21, Win10).
this code:
const maxon::Url url("https://www.mysite.com/myfile.xdl64"_s);
if (url.IoDetect() != maxon::IODETECT::FILE)
return;
returns the ssl certificate error in debug console.
The same code works in R23, R24, R25 (R22 did not check yet).