Wireshark is unable to capture any loopback communication (not just loopback interface) on Windows using WinPcap. You’ll need to replace WinPcap with Npcap to be able to do that.
Uninstall WinPcap first.
Select the following options (uncheck support for raw 802.11 traffic at your discretion) during Npcap setup
To capture loopback traffic, capture on the Npcap loopback Adapter