Perhaps you should manually update in a couple of steps, since your version (reported by your browser as 32-bit Firefox 72) is pretty far behind now.

For example, grab 32-bit Firefox 78.0.2 from here (this is U.S. English, for other languages, click the .. link and then click into the relevant locale folder):

http://archive.mozilla.org/pub/firefox/releases/78.0.2/win32/en-US/

Will that install? Then try the update again.

Note that in current release you can try to clear the startup cache via the "Help -> Troubleshooting Information" (about:support) page.

• https://support.mozilla.org/en-US/kb/use-troubleshooting-information-page-fix-firefox