When trying to download update I get the following on Windows 7-
XML Parsing Error: undefined entity
Location: chrome://mozapps/content/edownloads/unknown Content Type.xul Line Number 79, Column 54:
<description id="settingsChange" hidden="true">&settingsChangeOptions.label;</description>
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):
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.