French language Q&A Forum

Could you please explain why C'est and Il est seem interchangeable when in the lesson 'C'est vs il/elle est: saying it is/she is he is' these expressions have separate uses depending on context. Thank you.

J'ai acheté deux paires de chaussures, mais ________ me va.

I wrote "ni l'un ni l'autre ne", but it was rejected. It says it's "ni l'une ni l'autre ne". Now, I understand we're talking about PAIRS of shoes, not just shoes, and "un pair" is masculine. So is this an error?