If the data source column contains UTF-8 value, Maestro works fine.
UTF-8 values are displayed correctly in Maestro screen.
I encountered the same error.
I'm afraid current Beta doesn't support 'directory' name in Japanese.
I tried directory name like D:\test (all in English) then it worked. (file name should be English as well).
I hope it works.
The absolute path of my Excel file does not contain Japanese.
But if the column names of the Excel sheet contain Japanese, the error occurs.
The absolute path of my tfl file does not matter.
I tried the same kind of data, with column name with Japanese, and the error occurs.
And I also tried path in Japanese without column name without Japanese, and the error occurs.
*I tried beta 3, but the problem is the same.
*I confirmed data could be fine in Japanese with column name in English.
So column names, or path in Japanese seem not be supported yet.
In January I reported this as bug to Maestro team, so I added this as additional info
Let me share their reply.