What I have found, is that if one opens the .xlsx version of the Excel, directly into JMP, the cells with =concat() values in them are read in as a missing value.
If one uses the Excel JMP addin, the =concat() cells are transferred into JMP correctly.
If one copy/paste from Excel to JMP, the data are input correctly.
If the Excel spreadsheet is saved to a .csv format, and then the .csv is opened directly into JMP, the =concat() cells are correctly
I suggest that you use one of the alternative approaches that properly read in the =concat() cells as your workaround.
Jim