Have you tried logging the same request in assystweb?

The error messages in assystweb are usually better.

Also check the assyst user alias being used has permissions to link events.

Already in assystnet this happens.
It says it can't find the event builder.
I already checked here in the assystnet alias permissions and it already has all 76 permissions in the event privileges;

Could it be that the item/category/… of the task that should be created is either discontinued or not visible to the end users? The first task in the workflow will be ‘logged’ by the person logging the request so they need to have permissions to see all values used on the task.

I have a similar issue checking out Orders although I can’t confirm the error message is the same due to the language difference. Note below information from the Wiki advising of potential issues checking out Orders due to inconsistent use of mandatory fields: 

https://wiki.axiossystems.com/assyst11-5Wiki/index.php/Order_and_Cart_Set-Up

During checkout assyst copies the data from the Service Catalog's Order Forms to Service Request Forms, therefore it is critical to ensure that if a Service Request Form requires Mandatory data in any of its fields, that the corresponding field(s) in the related Service Catalog's Order Form are also Mandatory. If not, then there is a high chance the checkout will error when required data is not found when processing the Order.

Hello guys.

Thanks for your help.

MennovH and girvand, thanks for the tips.
But checking here, the problem still remains.
I don't know if I still need to configure something else.
We follow everything as it is on the IFS wiki.

On the 1st error screen, the item and category are not displayed. Is the Order registered via the service catalog or is the data informed during registration? it would be interesting to print the steps of the registry.