My PC Won’t Display on Monitor After Installing a New GPU—Any Ideas?

Hey everyone! I'm having a weird issue with my PC. Usually, when I turn it on, the power button lights up with a solid blue LED and a blinking red one, and my Logitech mouse lights up as well. But for the past day, when I power it on, the blue LED comes on, but the red LED never lights up, and my monitor isn't detecting any output at all. My mouse isn't turning on either. The only change I've made recently is adding a new video card since I was using an APU. I'm really puzzled by this, and I'd love to hear if anyone has experienced something similar or has any suggestions. Thanks!