Hello @UnsterKylink !
I put back my answer from the other post here:
For this one, as it is said there is a check to ensure the public key can be use for decryption and the private key can be used for decryption.
To make sure, it’s actually the case when validating the form there is an attempt for encryption and decryption done with the given key. I mean by that, that the server does not only check for the keys flags but is using the key to check if it’s truly usable.
It could come from the NTP yes, but apparently you’ve check that already.
Are you using the installer to generate the key pairs or did you import a custom one? If you imported your own, you might check if the key has been generated for decryption/encryption purpose.