I figured it out and if anyone else gets a similar problem, this is how it was fixed:
Left over registry keys from uninstalling Avast corrupted the fresh install. To avoid this, I used “Fix Issues” with CCleaner to clean my registry after uninstalling and before reinstalling. I don’t know what caused Avast to stop working in the first place, but if an uninstall is necessary, don’t forget to clean the registry! Everything is fine now.
Thanks for trying to help.