British Airways no on-line check-in

Dear all,

I hope someone can help me out here (BA phone lines are constantly engaged). I am going to Frankfurt from Edinburgh tomorrow. I had originally booked Lufthansa but my flight was cancelled due to strike action. I rebooked an hour ago with BA (via Heathrow). However, i am unable to check in online. Is this a bad sign and does anyone have any tips to make sure i get my seat? I can't be at the airport early tomorrow but could go tonight if necessary to try and get a boarding pass (however, my flight it at lunch-time tomorrow).

Thanks
Steve