PUB400: VSCODE/Code4i works, PuTTY does not

[SJLennon]

I'm not an expert is public/private keys, but a long time ago I created .PPK keys with PuTTY. And I've been able to happily connect to PUB400 with both VSCODE/Code4i and PuTTY without needing a password.

I can still connect with Code4i, but as of Feb 16, 2026 PuTTY says "Server refused our key" and defaults to needing a password. (Which it accepts and connects.)

I haven't changed anything on my Win 11 PC, so I don't understand why PuTTY has problems with the key.

Does Code4i do something different that makes the .PPK keys work?

I tried with PuTTY in Windows CMD and found this in the log:

debug1: Trying private key: C:\Users\Sam\Documents\Sam_tech\Certs\PUB400.ppk
Load key "C:\Users\Sam\Documents\Sam_tech\Certs\PUB400.ppk": invalid format

But this same key works with Code4i. Strange...