Check these points:

• The file must use a semicolon (;) between columns, not a comma; with commas the whole line is read as one field (the phone number), so no separate name is picked up.
• The first row is treated as a header and skipped, so do not put a real contact on line 1.
• Column order is contact;name — phone first.
• Numbers already saved as contacts are reused (matched after formatting), so duplicates are not created but are added to the list.
• The extension must be .csv ("File is not CSV").
• If a number in the file already starts with + (full international format), Sprwt leaves it exactly as-is even with Add country code turned on, so it will not be double-prefixed. Double-prefixing can only happen with numbers written without a + sign but that already include a country code digit (e.g. a US number typed as 11234567890) — re-import those with the toggle off after deleting the wrong contacts under the Contacts tab.