"Sorry, this conversation has reached its limit. Let's start a new chat."

I have been using Copilot for a while now, and it's not a tool that can be used for anything but simple short tasks.

Trying to use it for anything complex will result in the error you see. Which typically leaves the chat thread in a state where you can never reliably reopen it. So, all you work you have done is lost.

Medium complexity tasks where you have not hit that limit are equally compromised, as it's often impossible to re-open a thread and continue.  As Copilot will hang when you re-open the thread.

The only workaround is to break everything into a simple task and keep track when you have had more than a few interactions and know to stop. As you are close to losing everything you have done.

Ask for a document summarizing where you are and then start a new chat from that document.

Copilot is simply not ready for anything more than simple short interactions.