Locale controls how Power Query reads text during a type conversion. The text 03/04/2026 means April 3 in a day/month export, but March 4 in a US export. A successful conversion can still be wrong when both interpretations form valid dates. Inspect an unambiguous value, such as a day above 12, and confirm the source's convention.
Right-click a column and choose Change Type > Using Locale. Set both the target data type and the source locale. This reads the text; it doesn't translate column names or set the report's display format.
Decimal and grouping separators need the same care. A German reading such as 1.240,50 represents a decimal number, while a French export may use a space for grouping. Convert from the original text with the correct locale. Replacing punctuation by hand can damage otherwise valid values and makes the refresh harder to trust.