All references to OpenVPN are with respect to version shown in the image below and running under x64 Windows 10 OS.
OpenVPN Windows Client
We had seen the issue of connection error during an attempt to share gitlab and nextcloud resource with clients using Windows 10 and latest version of OpenVPN client, with a valid OVPN certificate.
Suprisingly, a Windows 10 lock up and need fro restart broke a perfectly working OpenVPN Client and reliably for some time. Following the crash and reboot Windows initially reported absence of an OVPN certificate and then failed to connect with the error message shown in the client2log file illustrated beelow.
All TAPs in use, error log
Tap adapters can apparently be created on the fly using the batch file supplied as part of the OpenVPN installation at the install location shown in the following image.
locate TAP creator
We note that the batch file must be run with Administrator rights, therefore right click addtap.bat file and run as – Asministrator.
That’s it! Be sure you have a valid certificate to the client you wish to connect with and select it from the GUI to initiate a connection.
Once complete the batch file process waits for a key to be pressed to complete steps needed to add a virtual TAP adapter, solving the problem.
batch process
We can further verify the installation or addition of the virtual TAP adapter by browsing Network Connections and noting a new TAP-Windows Adapter, v9#2 in this case.
add Windows TAP Adapter
The following resource was used during resolution of this problem;
https://jochen.kirstaetter.name/openvpn-on-windows-all-tap-windows-adapters-on-this-system-are-currently-in-use/