The 2.4  blink code suggests you didn't reinstall the RAM correctly or you put it in the wrong slot(s).  The first module should go in 2nd slot from CPU. If there's another module, it should go in 4th slot from CPU, etc. Push the module gently, but firmly, down into the slot. The retention clips should pop up on each end of the module and lock the ends in place.
I opened it up to check my ram. I pulled the ram card out and then put it back in and now the monitor says it has no HDMI signal and the power does not come fully on? It doesn’t completely boot up, if I unplug it and then wait it turns right back on instead of having me turn it on, if I hold the power button 15 seconds and it will shut down by the time I get to 30 seconds it comes back on, so it never actually stays completely power down. The monitor test is fine I don’t think I touched or unplugged anything so I’m confused. Again, I have unplugged it from the source from the monitor everything multiple times the fans are on, but it doesn’t power up the system.
XPS 8940, power not fully on