I came across a shia brother who doesn't believe in the authenticity of Ziyarate Ashura. My questions is does Ziyarate Ashura have a valid reliable chain of narrators

I would be grateful if you can mention a few references in English for me to read on the internet as I can't read books in Arabic ..

Yes Ziyarat Ashura is authentic.

For a technical analysis of it’s chain of transmission, you may see this Arabic page: