I think you should just retry using the button (bottom of the gmic panel next to the tickbox for Internet). On a fresh 2.3.3 install an hour or two ago, it worked. I can remember having a similar problem in the past, perhaps because I ran it in the early hours when the site was e.g. undergoing maintenance or backups.
Until you update for the first time you will not have all the available filters - that might not affect what you want to do, or it might prevent it.