The problem is here:
ChestText.text = false;
The error says that you are trying to store a value of type boolean, in a variable (property, field, member...) that expects a string value.
Luckily, in C# you do a
function call and convert the data to string. So, change your function to:
ChestText.text = false.ToString();
But again, what is the point of this? Maybe you wanted to modify
boolean to string. | C# Online Compiler | .NET Fiddle