It is not uncommon to run into these types of issues related to memory when attempting RAM upgrades. I would suggest always replacing both sticks (if applicable) with the exact same type of RAM, and please make sure the RAM is of the specifications of your particular Mac, PC, etc. I would suggest first trying to clear the NVRAM if you have issues after RAM install. TO do that: shutdown your computer, turn it on and IMMEDIATELY after hearing the hard drive kick, press and hold at the same time, the COMMAND, Option, P, and R keys. Hold the keys until your computer restarts.