There seems to be a disconnect when creating a copilot studio copilot. When you are first creating the copilot, the instructions for how the copilot is to behave field allows for 8000 characters this is great because it allows us to add more context and personality to the copilot, however, it will not work. You cannot deploy it.
When you go back in to troubleshoot you will see that the instructions field is now limited to 2000 characters.