MacOS – IKEv2 VPN not working after updating to MacOS Catalina – User authentication failed with username authentication settings

I think the unerlying issue is that Yosemite will not load kext (kernel extensions) unless they are signed by an authorized kernel extension developer. However in 10.8 and earlier, kexts could not be signed and signed kexts for 10.9+ will not load in <10.9.

I experienced the same issue loading unsigned tuntaposx for the vpnc cisco client.

You can override this behavior and allow the cpfw.kext to load in Yosemite by putting your computer into kext developer mode. This essentially reverts to the 10.9 behavior by allowing unsigned kexts to load.

sudo nvram boot-args="kext-dev-mode=1" 

Now reboot and your kext should load.

You can revert by doing this:

sudo nvram -d boot-args

The essence of the solution described there is plausible – that it has to do with the re-keying process which occurs periodically. You ought to see something in the Console log, and perhaps also in logs on the server side, that will point you in the right direction.

At random times during the lifetime of the tunnel, the two sides will re-negotiate the symmetric-cipher keys that they are using, so that the conversation does not continue to use the same keys for too long. If this process failed, the connection would be dropped, and if it consistently occurs "after eight minutes," this could well be it. All of the parameters on both sides must match exactly, and there's nothing easy about debugging IPSec. I'd start with Console as my starting point. (There are several logs – look at 'em all.)