FEFLOW | Error message "Invalid argument passed" when running FePEST

Question
Why do I get the error message "Invalid argument passed!" when running FePEST? The error message can be seen in - see Fig. 1

Fig. 1 - Error message when running FePEST

Answer
This error message is usually encountered by users from non-English speaking countries such as China, Japan, Greece, Hungary, etc.
PEST character requirements are very strict. Therefore, please check the name of the working folder and make sure that there are no special Characters in the file name and/or in the whole path, or symbols like:
<SPACE>
@
~
#
(
)