There is a very weird bug in the Audacity when the user tries to export the project to mp3. The popup box does not respond, loses the mouse focus, and can not return to the main UI.
Which exact version of Audacity are you using? (Look in “Help menu > About Audacity”)
Yes, if caianhua is using one of the affected languages (including Japanese and Chinese), it could be, but if I recall correctly, there were two relevant bugs. One of the bugs was in Audacity 3.0.0 and was fixed in later versions. The other bug was a Windows bug (introduced in a Windows update). The latter bug “should” be fixed if Windows is fully updated, but if not, Microsoft suggested a workaround here: KB4564002: You might have issues on Windows 10, version 20H2 and Windows 10, version 2004 when using some Microsoft IMEs - Microsoft Support
every version , 3.03 and 2.0.X all have the same problem ,I think this is a windows 10 system problem.My operation system is simple chinese character ,but I change it to American character for my windows UI. But the Bug is a frequent happening bug.Almostly can’t use the Audacity,I almostly to have a nervous breakdown. 
Edition Windows 10 Pro
Version 21H1
Installed on 1/12/2021
OS build 19043.1165
Experience Windows Feature Experience Pack 120.2212.3530.0
This is My window 10 version information.