Issue with plugin installation: Airplay, Chromecast & UPNP bridges and Material Skin

I was trying to re-install the Material Skin and Airplay, Chromecast, and UPNP bridge plugins after a long time, but the system seems to be stuck in some kind of a loop. Everytime I click on the plugin page, it pauses for a few minutes and then asks me if I want to restart, and no matter what I select, it keeps going pack into the same loop. A look at the server log suggests that these plugins could not be downloaded. I've attached a snapshot of what I see.

I'm running LMS on MacOS. Relevant details on the setup are:

Logitech Media Server Version: 7.9.3 - 1579448956 @ Mon Jan 20 04:10:14 CET 2020
Hostname: XXXXXX
Server IP Address: X.X.X.X
Server HTTP Port Number: 9000
Operating system: OS X 10.10.5 - EN - utf8
Platform Architecture: x86_64
Perl Version: 5.18.2 - darwin-thread-multi-2level
Audio::Scan: 1.02
IO::Socket::SSL: 1.966
Database Version: DBD::SQLite 1.58 (sqlite 3.22.0)
Total Players Recognized: 2

I tried to look for these plugin folders in the following locations, but found nothing:

Plugin Folders

/Users/xxxxxx/Library/Caches/Squeezebox/InstalledPlugins/Plugins,

/Users/xxxxxx/Library/Application Support/Squeezebox/Plugins,

/Library/Application Support/Squeezebox/Plugins,

/Library/PreferencePanes/Squeezebox.prefPane/Contents/server/Plugins

Any suggestions to clear these from the update list?

TIA,

Nikhil

Attached Images