If you upload a contact template with the phone numbers in a format other than just digits (Ex: 503-123-4567), it can generate an error and not upload the contact list. To fix this, you will need to change the phone format to only have the phone digits (EX: 5031234567)
You can do this on a spreadsheet quickly by using the following steps:
1. Create a new column with this formula as it's value in the 2nd row
=--SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(D2,"(",""),")","")," ",""),"-","")
2. Drag the formula down to cover every row
3. Copy that column and paste as value in the original phone column
4. Delete the formula column
5. Save and upload the new spreadsheet