I have figured out what was wrong. I'm writing this here in case anyone else might have a similar problem then mine.
I tried uninstalling and reinstalling Avast, and the update issue still persist. Luckily, if I try to uninstall or update using "apps menu" in the Windows system settings, it gives me an error log. From the error log I concluded that the reason my Avast wasn't updating is because of connection issues, specifically timeout issues from IPv4 and IPv6. I'm no network expert, but I know that these can be related to DNS settings in windows network settings.
About a week ago, the DNS provided by my ISP was giving me connection problems, so I changed the DNS to Google DNS. (8.8.8.8 and 8.8.4.4) and resolved my connection problems. For some reason though, the Avast software wouldn't allow me to update with the Google DNS. I switched it back to my default ISP DNS, and the software updated itself, along with the Virus Definitions.
So that resolved it.
I do have a question though, and this is more aimed at people from AVAST (whom I hope is looking at the forums) :
Is there any particular reason why using Google DNS would prevent me from updating my AVAST software? I also tried some other reliable public DNS, like Open DNS, and Cloudflare, and it seems that AVAST won't let me update if I use those either. I'm genuinely curious because other softwares I installed had no problem updating using the Google DNS, or the other I mentioned.