[rhelgeby]

error 012: invalid function call, not a valid address

Some additions to the description:
The symbol is not a function. You've used a variable name as the name of a function, usually after renaming a function to a name that's already used by a variable.

It might be hard to figure out such errors, because it cause a lot of other side effects that might confuse people. Sometimes it helps to just comment out code that the compiler is complaining about and see if there are other errors that should be fixed first.