IMPORTANT: There is a quirk with using Microsoft Excel when exporting Facebook Page User IDs (UIDs).
The issue is that Facebook page UIDs are 16 digits long. However, Excel only maintains numbers up to 15 digits.
CLICK HERE to learn how to create custom audiences with LeadKlozer.
THE EXCEL SOLUTION:
Just download the .csv file and don’t edit it in Excel before uploading the file on Facebook to create a custom audience.
You can open the .csv file to copy the Page ID that will be needed during the custom audience creation process…but simply don’t edit the file.
MORE ABOUT THE PROBLEM:
You can see in the images below from the Excel and Apple’s Numbers applications that each cell containing an individual lead’s UID can be seen just fine in Apple’s Numbers program. But the same info looks like 3.475575+15 in Excel. When you click on that cell in Excel, the real number is revealed, but the 16th digit is always set to zero, rendering the lead’s UID invalid.