Nessrine Hamrouni Thanks for reaching out. As per the screenshot it looks like your logic app workflow is calling azure function and the logic app is failed after 4 retry calling your function endpoint and it fails with the 500 error.
This doesn't look like authentication error rather your function is having issue executing. I will suggest you to test your function app directly and verify if it is being successfully executed. Further I will suggest you to review the application insights log to know more details on the 500 errors. You can always leverage the Diagnose and solve problem blade on your function app to troubleshoot the 500 error and the action plan to resolve the issue if there are any.
Feel free to get back to me if you need any assistance.
Thanks a lot I will send you an email to schedule a confcall to help me many thanks :)
I resolved the issue by granting the permissions to the managed identities under the app which I'm using :)
Thanks for your reactivity and support.
Have a great day