Whereas it was OK with APP1.4.2 (but only when fisheye lens input info is manually forced), with APP2.0.0 the calibration window for circular fisheye remains empty and additionally the EXIF button yields a wrong "No image" message.
Ironically, APP2.0 (unlike v1.4.2) is now able to recognize the camera/fisheye lens combo EXIF info and to report them on the Parameters window table. This is not however without a strange interpretation: e.g. 10.5 mm becomes 9.84 mm. Fortunately the subsequent steps of the work flow are somewhat not hampered.
Yet, when the lens EXIF isn't available, it looks like APP2.0 makes a (wild) guess about focal length that is "not too far" from the truth... Manual correction of the inputted lens data makes the detection and rendering better and thus very good.
Anyhow, the circular (or full frame) fisheye lens calibration ability is an essential tool that seems to be missing right now.