Not entirely certain what's gone wrong there, but I would suggest the following as a recovery:
- Close all running Wireshark instances, and anything else that might be using npcap (e.g. nmap), even better to reboot.
- Uninstall any installations of npcap and WinPcap you find in the list of installed applications.
- Reboot.
- Ensure there are no installations of npcap or WinPcap left in the list of installed applications, if any found, repeat from step 2.
- Install the latest npcap from their website, currently 0.996.
