My Ubuntu has a problem that won't let me download newer versions of the browser (or any software).
Often, this is caused by lock files in the temp folder. If so, you can manually clean these up. There is also a cleanup routine you can run.
Another possible issue is the distro/repo. If your distro is too old, you can't automatically install updates, unless you fix the repos. That's a pain. If this is the issue, you can use wget to manually download software, then manually install the software.