Before the v.5.0.x,during runing ~ visual previews~ step ，it can show the percentage ，but  in v.5.0.6 it can't show the percentage. Why?

https://drive.google.com/file/d/1e6ELm-w...sp=sharing

In your screenshot the visual previews are finished. That's why you don't see any percentage.
You will see the percentage display and remaining Visual Previews only while they are being generated, not if you are loading a sequence where the cached visual previews are being loaded.

While visual previews are being generated，it also can't show the percentage ,Why?

It should do.