Change the Trace Channel on the select node to Weapon, location at the top of the screenshot.
Next replace your current nodes with the nodes highlighted in the image below, locations at the tops of the screenshots.
Next copy the video below in the BP_MasterAIController.
Next go to the EQS_RangeAttack and select the Trace: TO QC_AttackTarget node like in the image below and set the Trace Channel to Weapons.
NOTE: If you are using a custom player character or have migrated Smart AI to another project make sure that in your players character blueprint you select the Mesh (Inherited) component.
Then in its collision settings make sure you have the Weapon channel set to block like the image below.