hi guys! could really use some help here with some PC issues im having

i got this PC secondhand and ive only had it a couple weeks- was working absolutely fine for a couple of weeks and then started acting up

• originally it was just turning on but not booting.
• BIOS speaker gives no code with all components, just has a clicking sound
• when one RAM stick is removed, the BIOS speaker gives a beep code of, which, according to my research, means power supply problems
• i got a new PSU entirely, however i am still getting the exact same issue with the new PSU.
• cables are all in tight as they can be. have tried multiple outlets too- nothing working

does anyone have any idea what else the culprit could be? im just really confused to still be getting a PSU beep code when its a new PSU, and only when its just one stick of RAM

thank you in advance!!