Hi, I posted your question to Discord, because there are more people frequenting that nowadays. I personally don't know how to solve this, but over there we have plenty of tech savvy people being able to help you out. If you want, you can also join the Discord server and get your answer to this, or any other question you may have. Here is the link: https://discord.gg/hU878P4 See you there hopefully!
Sounds like something got borked in your environment. Maybe try reinstalling / updating your version of .Net framework, not sure which version is required for the launcher though?