I just tried placing an XLSX file (created in LibreOffice Calc 6.3.6.2) in Publisher 1.8.3.641. A table with the appropriate number of rows and columns was created, but all cells were empty (not white text on white background, but actually empty) and the table frame/border/boundaries were all set to no-stroke. On the other hand, when I try to place an XLSX file with colored cell backgrounds, it creates a table with appropriate cell colors. The files open just fine in Microsoft Excel 2013, showing the expected cell contents. Windows 10 Enterprise version 1809, 64-bit.
So I'm a bit mystified by what I might need to do (besides File > Place..., select the file, and click on the page) to get the data to actually populate the newly created table. Presumably this works for others?
Temporarily, I am copying the data from the XLSX file and pasting it into a Publisher table.