Hello Aleks,
Trusted RFC Connection is a most important RFC Connection in SAP Solution Manager. This connection always allows for a seamless integration of both systems involved. i.e. You can log on to one system (for example : Solution Manager System) and work within other system (for example : ERP System) without logging on again. Hence this connection is only used in such cases where an integration is necessary.
If there are any errors in the use of an RFC Destinations then 'No Authorization to logon as Trusted System' occurs. Pre-requisite for using Trusted RFC Connection includes assignment of authorization object S_RFCACL in the SAP Solution Manager and Managed System User.
Standard SAP Roles SAP_SM_S_RFCACL (SAP Solution Manager User + Managed System User) and SAP_SM_BW_S_RFCACL (BW System User) are available which in turn contain authorization object S_RFCACL. Please note SAP_ALL Profile does not contain this authorization object by default.
Please provide these roles and then let's check if your issue gets resolve.
Regards,
Omkar Kuldharan