If the browser keeps crashing upon launch, you can't really do anything to fix it, and in order to get an alternative browser you'd need to download it -- using a browser. Here are a few things you can try to fix your current browser, and there's even an alternative way to obtain a different browser without using a browser…
Aug 06, 2011 Solving Technical Issues - Roll20 Wiki May 15, 2020 Why won't Java Applets run in my web browser? - Quora Thanks for A2A I think the main cause to your problem is that Java is not enabled in the web browser. If Java is already installed but applets do not work, you need to enable Java through your web browser. The procedure is as follows for some How to Fix Some Websites Not Opening in Any Browser Issue Jun 14, 2020
Blockers built into your web browser Internet Explorer 6 and higher, Firefox, Safari, and Google Chrome all have popup blockers built into the applications. See below for instructions for specific web browsers. Blockers you add through a toolbar Some of the most popular web browser toolbars, such as Google Toolbar and Yahoo!
Aug 06, 2011 Solving Technical Issues - Roll20 Wiki May 15, 2020 Why won't Java Applets run in my web browser? - Quora
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Error Solved: Browsers Not Working after Windows 10/8/7 Dec 11, 2018