Hi Jim,
Did you also use a VirtualBox guest to test Npcap 0.04? I think the cause is the same with Pascal: I added Winsock Kernel init code to loopback interface's OpenAdapter op, if the init fails, the adapter fails to be opened. There're also two ways, first provide me the reproduce steps if you think it's viable. The second is to use the debug version, I have updated the version to 0.04-r2, you can use the debug one and give me the DebugView text I documented for Pascal.
Improvements in Npcap 0.04-r2:
1) Wireshark now can see Npcap version 0.04 instead of 0.03.
2) Added some trace message for WSK.
Lastest installer:
Lastest debug installer:
Cheers,
Yang