Copy a project

I created Default Projet or Model (Modele in French).
The problem is I cannot copy it. I have an error message (see attachement).
I put a date and charge in every task (it should'nt be necessary in a model anyway...) but I still have this message.
I tried to cha,ge the type of projet but I still have the mesage.
And I can't see where is the problem.
Can you please help me ?

There was some task with a validated duration of 0. Wich is normal if the task is "planification" for example. So I solved my problem but there is still an issue. At least the error message should say where is the problem (which task).

This isn't an error.

You use the planning mode "Fixed duration" who forcing you to set the duration date.

If you want don't see the message anymore, change to a floating planning mode.

May be the "project template" feature can be improved for fixed planning modes.

thanks for your answer.

I can set the planning mode on a task but I can see where you can set it on the project?
Because there was no error on tasks. Only on the project when I tried to copy it.

I did another try and I have the same message. I refreshed everytask, replanified, and still no task in error. This time again I have a validated duration at zero, to planify as soon as possible, with a planified duration of 1 wheras the begin and end date are the same.