Since updating to InDesign 17.0, data merge will not work. One particular .csv file doesn't respond and another .csv file causes the entire program to crash. I deleted InDesign and reinstalled, with removing all preferences and still not working.
Open the IDML in InDesign Save the file as a new InDesign file with a new name See if the issue persists.
Try resetting your preferences: The easiest way to reset everything is to delete the InDesign preferences: as soon as InDesign starts to boot hold down Shift, Alt, Ctrl (and Apple/Cmd if working on a Macintosh). A dialog will appear asking to delete the InDesign Preferences, select 'Yes' on this dialog. Further info and instructions here if needed: https://helpx.adobe.com/in/indesign/kb/indesign-preferences-support-file-locations.html