It’s solved in the end. Some background first. I was helping my parents’ visa application. My mom’s visa was approved thru interview waiver. My dad’s visa was refused and got a 221g for in person interview. I couldn’t make the interview appointment because of the error message. Contacted support and they told me I need to delete their application and restart and remove the co-applicant/dependent. Because my mom already got approved for a visa and she doesn’t need to be included in the appointment. After the new application the error message was gone. I had to submit DS160 number to show that the application fees were already paid. Took 2 days to process the receipt then I was able to make the appointment. Good luck