Hi @fatemehdashti, the user account used to connect Power BI Reporting Services Service to the Report Server database must be, at least, member of the SQLAgentOperatorRole on msdb database, in order to create jobs. (refresh plans create jobs internally to deal with schedules)
Can you check that? It is a permission on the server that hosts the Report Server database.
On your report server configurations, the connection is made with NT AUTHORITY\Network Service, but you gave permissions to NT AUTORITY\SYSTEM. They are different users -> I believe that this is the problem.
Why don’t you try to change the database configurations of your report server to use the built-in suggest account (more secure)? Or create a database user for your PBIRS authentication?