it appears only to the user who did the update method using his token

Most likely because your activity is configured to have only 1 slot (default) and you call the OpenWorklistItem method and not setting the Alloc parameter. The default behavior is to allocate a slot for the task opened by the user (Alloc = true). You will also notice that the status of the Worklist item for the user who opened it, changes to Open. If you want to allow other's to open, set the Alloc (which stands for Allocated) to false.

Note that this behavior is by design, it prevents users from doing double work. 1 slot = only 1 user should completed the task, 2 slots = 2 users, etc.

Thanks

that really solved the problem!!!