Hi, I have installed Processing 4.5.2 on OSX 15.7.3, but I can’t get the Contribution Manager to query any libraries. Modes, Tools, Examples and Updates are all blank too. It looks like it cannot connect to the internet at all - browsers etc all work fine. Any ideas?
Welcome to this forum. 
I have just installed Processing 4.5.2 on OSX 15.7.7 and the Contribution Manager displays Llibraries, Modes, Tools etc. so I don’t know what is causing this issue on your computer. Sorry I cna’t help further.
I had a similar issue once, and it turned out to be a network problem rather than Processing itself. If you haven’t already, try checking whether a firewall, VPN, proxy, or antivirus is blocking the connection. Testing on a different network can also be a quick way to narrow it down.
You can also always check https://processing.statuspage.io/ which tracks (among other things) the availability of Processing’s Contribution Manager.