The export log shows a message like this:
Skipped Product: 1/0 The reference "XXX-YYY " is incorrect
This indicates that the product reference is not compatible with Amazon specifications, the reference you’re sending, contains one or more invalid characters for Amazon.
To be valid, a reference must contain any displayable ASCII character, being composed of 40 characters and without spaces at the beginning or end of the string.
The filter being very tolerant, this problem occurs very often when the reference has a space at the beginning or end of the string, in this case use Import and export tool to clean your references.