A large invalid count usually means file content does not match validation rules. Importers commonly inspect market, length, character type and structural completeness, rejecting a row when any requirement fails. An ordered local review is faster than repeated uploads.
First align selected country or region with every number. Length and prefixes differ, and mixed country-coded and local forms can invalidate a batch. Prefer one market per upload and one documented international or local representation.
Next inspect length and characters. Names, company text, notes, symbols, full-width digits, plus signs or separators may be invalid in a field that expects digits only. Keep only the number column, normalize character width and remove unsupported decoration.
Remove blank cells, empty lines and truncated rows. Spreadsheets may convert phone values to scientific notation, alter final digits or strip leading zeros. Set the column to text before paste and flag values outside the market's plausible length range.
Then verify encoding and delimiter. Garbled headers or content suggest UTF-8 versus legacy encoding damage. Save a clean CSV or text file with one delimiter and no mixed comma, semicolon and tab structure.
Finally deduplicate, ensure the header was not imported as data and sample the first rows against the source. The repeatable sequence is market and prefix, length and digit validation, empty and truncated removal, encoding and delimiter, then deduplication and header review.
