why cant my computer search for gigantic files?

Your screenshot shows Portuguese File Explorer using the English query size:gigantic, so a language-dependent search keyword is worth checking before repairing Windows. Microsoft documents that friendly search labels depend on language, while canonical property names avoid that ambiguity. In the same drive, try System.Size:>1073741824 to search for files larger than one gibibyte without using the named category. Allow the search to complete. Then repeat inside a folder containing a file whose size you have verified in Properties. If that works, narrow or widen the numerical threshold to suit your needs. If it still returns nothing, search for that known file by name in the same folder and compare the results. Check indexed locations and exclusions only after this controlled test. An empty result alone does not prove that the index is corrupt or that Windows cannot search large files.