Using IBrowse version 2.4 under 3.9 and 2.4 OEM under OS4.0, I have the same problem.
Google thinks I have disabled cookies, which I haven't.
Have also tried Aweb under OS4.0, same result.
On logging in on AmigaWorld, I get a message thanking me for logging in, but it doesn't log me in.
Can log in here ok.
Have flushed the cache but no change.