Wildly Agonising Guess: Power down, unplug & replug each end of the floppy data cable, unplug & replug the drive end of the floppy power cable, put a known bootable floppy into the drive and reboot. Go into the BIOS setup program & verify that it is properly set up to boot from the floppy first & that it has recognized your new RAM. Exit Setup, saving your changes if you made any.
If your system now boots from the floppy your problem is probably solved but you may still need to verify that the RAM is working properly. Try running memtest 86. If the system won't boot from the floppy then the floppy drive may have died; test it in a different system or replace it with a known good drive.
Keep in mind that malfunctioning RAM can make anything in the system appear to be malfunctioning.
Good luck!