Most searches fail because the file you obtained is likely a repack of the 4K remaster or a European Blu-ray rip. The English track was either never included or was removed by the uploader.
By using MKVToolNix to remux a proper English stream, you are not just fixing a file; you are preserving a version of the film that is slowly disappearing from digital storefronts. Do not let a missing audio track ruin Ofelia’s journey through the labyrinth. Pan 39-s Labyrinth English Audio Track Download Fix
The issues with downloading the English audio track for Pan's Labyrinth can be attributed to various factors, including: Most searches fail because the file you obtained