Random 'IKE authentication credentials are unacceptable'

DamonC-0774 15 Reputation points

I've had a bit of an ongoing issue, that I haven't been able to resolve, I'm hoping someone has seen before (or can offer advice).

We have an Azure Virtual Network Gateway for P2S connections. The authentication certificate, and connection itself are pushed out through intune configurations - which seems to work without issue.

The certificates are issued through an on-prem AD CS server, which utilises the Intune certificate connector to provide the certificates.. Once again, this seems to function without any issue - intune shows the server as having a healthy status.

However, we randomly find that machines which are used remotely 100% of the time will fail to connect, using a remote command window through our RMM software to try and dial the connection (rasdial) we get this:

Connecting to VPN Connection... Verifying username and password...
IKE authentication credentials are unacceptable

Now, the odd part is, tomorrow, without any intervention it will start working again. I can see that the certificate is still on the machine, and is still valid. I've tried deleting the certificate, and revoking it on the AD CS, to no avail.

The certificates have a 2 year lifespan, and haven't expired.

Any advice here is welcomed.

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