Computer stopped working in standby mode

I left my computer alone for about 40 minutes and then came back to see that it was in standby mode. I tried pressing buttons on my mouse and keyboard and it did nothing so I went for the reset button assuming my computer hardlocked. It would then not turn off from the power button as well as the reset so I turned it off from the PSU. I turned it back on from the PSU and pressed the power button and It launched. But the mouse and keyboard didn't light up and the screens were blank and I still couldn't turn it off from the power. Help...

Make sure all connections are tight. Might just be a loose connection at the back or inside