Tuples working on functions but not in method / data directives?

I’m reaching out because I’ve encountered a peculiar issue with using tuples in Epicor and was hoping for some guidance. In functions, tuples work perfectly fine for me. However, when I try to use them in method or data directives, I run into an error. It says, “Feature ‘tuples’ is not available in C# 6. Please use language version 7.0 or greater.” Has anyone else faced this? Any idea why this might be happening or how to resolve it?

Sample code:

List<(string update, string preUpdate)> primaryBankChangedPairs = new List<(string, string)>();

I had checked import and everything looks fine.

Thanks!