Problem
A chart in your report displays an "Invalid field name error."
Why it breaks
Certain connectors support characters in their field names that Looker Studio is unable to process. For example, Looker Studio does not handle BigQuery fields that contain Unicode characters and special characters like ampersands, colons, and so on.
Learn more about BigQuery flexible column names.
Solution
To resolve this issue, rename the fields from the underlying dataset and then reconnect the data source.