Data imported from Excel (CSV) truncates into multiple columns even though it is one column in Excel

I want to import data that I exported from another program into a CSV file, then examined in Excel. In Excel the data displays correctly–I only need one column. But when I import to a new board in Monday, it truncates into mulitple columns. Interestingly, I already have a board I created from an import of similar data from the same program, same process, that worked correctly. How do I prevent the truncation?