If you've done a bulk candidate import and not all the candidates in your CSV file successfully imported, check the Data import/export activities page in the Backoffice (Settings > Data import/export activities) to review the reasons why.
There are two possible reasons why a candidate may not import:
If a candidate already exists in the vacancy you are trying to import to, either as a submitted or an unsubmitted candidate, the candidate will be considered as a duplicate and will not be imported.
Check the candidate's email address in your CSV file and then search for that email on the Person list page to confirm this. Click the Person audit trail icon to view submitted and/or unsubmitted applications and confirm they already exist in your vacancy.
One common scenario here is that users sometimes forget to select the option to submit candidates when importing. This will import the candidates as unsubmitted candidates, after which they may be contacted and asked to check and submit their own applications.
If you don't want to contact the candidates (or mimic them and submit on their behalf), you may use the Delete candidate option in the Bulk action menu on the Unsubmitted candidates page to delete the candidate(s) and then re-import them, making sure you check the option to submit them the second time.
Candidates who end up in the failures list can't be imported for some reason. This is most likely either due to some invalid data in the CSV file, or due to the CSV file format not matching the format required for import.
Make sure the file you are importing matches the format required. Click the Download CSV Template button on the Import candidates to this vacancy page (Vacancies page > Icon in Functions column) for the required CSV import format.
If the import format is correct, it's likely that there is some invalid data somewhere in the import file - usually this will be one or more characters in a text field somewhere. Most commonly, invalid characters may be found in text fields with lots of text in, so check these first. These characters are usually obvious in Excel as well as they won't look like letters, numbers or commonly used symbols. Check also for the \ character, and replace with the / character if found.