When you are doing Onboarding/Bulk Upload and you encounter red boxes (error) on some values, check these errors by providing the correct one (either from selecting from the drop down or entering it).
There could be times that you have already corrected it but still showing error, this might be coming from the spaces before the First letter or after the Last letter of the value. Remove the spaces in the sheet and upload again.
Note: This is a known issue in the system and solution is already lined up. In the future, though your sheet has the spaces on it, this will be automatically corrected from the background so you can proceed in uploading the sheet.