My Galaxy S8 Can’t connect to my PC thru USB.

I connect my Samsung Galaxy s8 to my computer very often to transfer files. Everytime I connect it I cannot open files until I go onto my phone and press ‘allow access’ on the pop up. However, I must have accidentally clicked ‘deny access’ or something as the pop-up no longer is there when I connect my phone to my PC. My phone charges, but there is no sign of it being connected to my computer. Any suggestions?