A lot of people report tinnitus when they are hypo. It's unlikely that your previous med "stopped working"; more likely that you needed an increase or that you needed to add a source of T3 to it. Many report that when their thyroid levels are right for them, the tinnitus goes away.
Do you have recent lab results? If so, please post them (TSH, FT3 and FT4, along with the reference ranges, since these vary from lab to lab, so must come from your own report.
There is a lot of research on all of this, but you are right - each of us is different, and will react differently to at treatment, so it does vary greatly from one person to another. What's right for me, may not be right for you.