Cheers everyone, I just kept persisting and finally it worked. Documents were merged and compressed (about 1.5 MB), I wasn't using a VPN, cleared cookies, refreshed....the lot. But for some reason, 24 hours later it just worked.

I guess my only advice is, there are glitches, so just keep trying.

Thanks to everyone with advice, much appreciated.

Yea, I've done that about 20 times now, I'm running out of ideas. Weird that the 403 error disappeared and let me upload to 2 categories, but still won't work for 3. Current location. Just logged out and back in again now, but still won't upload. Maybe I'll just try again tomorrow, I've refreshed and cleared everything I can think of.

Thanks, I cleared all browsing data, cookies and refreshed the page (as per helpful comments above) It now allowed me to upload 4 and 5, finances and employer details, but it still won't allow me to upload (or drag and drop #3 - my summary and current location) so I'll keep trying to clear up, refresh etc and see if it will have a change of heart.

I've merged and compressed my pdf's so they're all under 3 MB. It's been like this for 2 days and I don't know what to do next. I've messaged them, but no answer.

I'm using chrome