Can you go to your browser console and create a function like:

function f() {
let value = "; " + document.cookie;
    let parts = value.split("; " + "sIRTFrontend" + "=");
    if (parts.length >= 2) {
        let last = parts.pop();
        if (last !== undefined) {
            return last.split(";").shift();
        }
    }
    return undefined;
}

And then call f() and tell me what it returns