Some ATS systems are not very sophisticated and confuse your text in the two columns and mix them together.
So, one-column resumes are easier to scan by the ATS. Two-column resumes make resume parsing far more difficult and more prone to errors. It’s not an inevitable conclusion, but it’s one that you might not want to risk!
Using a more straightforward format will make this easier for the machine to parse and differentiate key information. Single-column resumes are easier to make a clear delineation of the company, job title, dates employed, and responsibilities. However, newer versions of ATS can read both single- and multi-column resumes.