Cant really make it more mwe than that
I presume the file above was saved as TestLyx.tex and not in an unusual folder path.
Presumably in a documents folder under your user name, and that user name does NOT have accents spaces or other non-latin characters)
Lyx needs to be installed correctly such that using the tools check tex it confirms all is well with TeX.
LaTeX (plain) and it should have shown as
The message as shown should be Importing .......tex2lyx -f "TextLyx.tex" "TextLyx.lyx"
NOTE you either have a typo or there is something drastically wrong since there should be a space between
messages pane to check there is a space if no space you need to consult Lyx support
Proceeding on the basis it's a typo within your question and there is a space, then why do you get
An error occurred …
The most likely culprits are
1) something bad in the tex file, unlikely but not impossible so ensure it is a very simple cut and past file (as I did with notepad)
2) file is on a bad path (please include such detail in your question)
3) tex2lyx is on a bad path
go to a cmd prompt (use any means but avoid starting within the LyX folders) and run
>where /r \ tex2lyx
Confirm both are exactly the same answer especially the path before tex2lyx
Tell us what those paths are (just the once)
However I can tell you even after a week of trying hangul characters may not work and had to resort to a fresh user account.