For Agentless monitoring the Agentless injection needs to occur before the Synthetic injection. Can you try moving the Agentless injection further up your page? Also, are there are any restrictions on when you add the agentless injection? Possibly the page is not meeting the criteria.
Yes, there is a restriction. The aplication is on storage account, that is not compatible with oneagent. The Agentless injection occured first of all, so i really don´t know why the synthetic user does not appear in the application.