wanezhiling, you haven't yet answer whether your mkvextract is running with non-English language.
Your screenshot clearly shows that you are on Chinese Windows, so your mkvextract will very likely be in Chinese, too. Try running it in command prompt and watch the output. The language setting in mkvmergeGUI works for MMG only, the command line tools will run in your system language if there's a matching translation, unless you force --ui-language.
And I guess your issue is the same, STaRGaZeR, since your Windows doesn't seem to be English either.
As far as I can see, currently gMKVExtractGUI doesn't force mkvextract English, and can't catch the progess info if the mkvextract output doesn't contain the word 'Progress'.
Try the suggestion above in #81 to make the translation unavailable. If that works, then that's where the problem is, just wait for an updated version, which I guess will come soon
