FileMaker Pro 16.0.3 (but probably from 9 or older)
macOS 10.11.6 (but probably from 9 or older)
iMac (Retina 5K, 27-inch, Late 2014)
Some text data seem to be impossible to import correctly from an Excel file, just because they seem to be numbers, even if they are definitely not in the Excel sense of term.
As an example, i tried to import a price list from a provider where some Item's code are like 12E105; it failed, because FileMaker was importing values like 1.2e+106 instead.
Yes, it is a text field and yes, Excel is seeing this cells as a text cells.
First save the file form Excel to a text file (like.txt) and then, import this file to FileMaker.
Even if unnecessary, i attached sample files.
REMARK : <SELF-CENSORED>