It was a simple drag and drop of the new 1.15.2 update into Valhelsia 2 (which is a 1.15.2 modpack) mod folder. I am unsure if other steps needed to be taken, but just assume I wouldn't know to do x. So, probably less of an issue and more of me just being clueless.

Do you have a crash report/latest.log?

Need a crash log

I wasn't able to find the launch report from before so instead I tried launching again. This time it requested Observerlib 1.15.2 which I downloaded and also moved into the mods folder for Valhelsia 2. It was able to launch successfully and get into the start menu. I loaded my save just fine but when I went to open JEI it crashed.
crash-2020-08-19_16.26.57-server.txt

That crashed because of a bat.

I'm not sure that this is AS' or ObserverLib's fault