As far as I can see, no special characters, no numbers first, no spaces etc.
no idea why one would have to do this, but otherwise excel edits don't update, even if you remove .xls -fiele and add it again)
I just had the exact same problem with exporting a joined table and getting an empty feature class. I used the copy features tool instead and it worked. Go figure.
I find it helpful, sometimes, to export the xls(x) to csc and then open in notepad to edit. Then join the csv, not the excel file.
I had the same problem. Copy Feature solved it in the best way because I can not edit the joined layers.
I had the same issue. It's been solved by saving the table that you want to join with the Feature Class in CSV (Comma delimited) format, and then redo the Join and Export the data.