Unable to access ~/Downloads folder

Further to my original post, I have:

Deleted and re-created the ~/Downloads folder
Restarted Firefox in trouble shooting mode
Installed the Iridium browser - same problem.

Again, I have changed nothing other than upgrading to the latest
snapshot this morning.

Thanks

Other than upgrading to the latest snapshot, I have changed nothing on
my Lenovo X1 Carbon 6th Gen.

When I try to download anything using either Firefox or
Ungoogled-Chromium I get:

The folder contents could not be displayed
You do not have access to the specified folder

Does anyone have any suggestions as to the cause or a fix?

Thank you