File upload does not work anymore on any browser

Give this a try: boot into Safe Mode according to How to use safe mode on your Mac and test to see if the problem persists. Reboot normally and test again.

NOTE 1: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

NOTE 2: if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode. This makes it act as a wired keyboard as will insure a successful boot into Safe Mode.

emabolo wrote:

settings are controlled by my company

There are other settings that you may not be able to see or change that can impact this. Your company might have disabled this capability intentionally, or it might have inadvertently done that and did not intend to.

I would check with your company's IT department to explore what might have happened. My work computer is managed by my employer and they have disabled certain things (on purpose), especially iCloud Notes and some other things, including some Siri functions. In your case they might have restricted downloads from certain domains or it is possible other parameters in their configuration interacted with the latest MacOS upgrade to create unintended results. So I would check first with them.

I know, but on the Firewall settings I don't see different settings for the 2 directions. It only says "allow incoming connection".

Turn the firewall off completely and test. It is useless unless you are on a public network, but then there are better ways to avoid those things. I can't see how it would create the problems you are experiencing, but it causes all sorts of other problems.

After you complete testing with it off, you can turn it back on.

Another test you can try is to startup in Safe Mode and see if you can upload in Safe Mode. If you can, then you have some third-party system modification causing the problem.

Have you disabled the Firewall?

Are you using any vpn?

OK, by upload which direction of file transfer are you speaking of, upload is intended to mean sending a file from your computer to somewhere on the internet.

OK, Download is the proper word to eliminate confusion.😀

Have you given Al browsers Ful Disk Access?