in my case, i got the card first and then the bank account. I had already created login ID for my card by then. Bank account opening was online. One of the last few steps asked me to create a login ID in case I did not have one. This step, I skipped (there was some text which made me think it would lead to some sort of duplication. I do not recollect now what it said.) Then I logged in with the card login ID and selected the link bank account option. This failed in the first attempt but a few hours later when I tried again, it worked. Pretty smooth from then onwards.
Most people have gone the offline route and found to be a more reliable method.