I stumbled upon this error when I was trying to fetch items from SharePoint List using REST API. The query to field 'ExpandColumn/ColumnName' is not valid After a quick research, I found that we get this error if we are trying to fetch multi-line text column through $expand query. What does it mean? If you have a lookup column, and if you want to fetch columns through a lookup column, you can use $expand query. Though it works for fields such as Single line of text, Date, Numeric etc, this $expand query will not fetch multi-line text columns. The workaround for this limitation is you would need to make two REST calls - one to fetch the List items, and the other to fetch corresponding multi-line text value from the lookup list directly.