The following endogenous variables aren't present at the cur

Dear Dynare Users,

whenever I get the following error message:
"The following endogenous variables aren’t present at the current period in the model:"
What do I have to do?
Can I solve the problem by setting the respective variable as a predetermined one?

Predeterminedness per se does not help, because it makes a variable timed (-1). Generally, if you get that message, there is a timing problem in your model, because your model does not determine the current value of the respective variable.