online check in problem

Can anyone help pls.

Ive been trying to check in online for our flight to SF tommorow but every time i try i keep getting this message

"Were sorry
Unfortunately we are unable to check you in online. This may be because you do not have an ESTA or you are a valid US visa holder."

Ive filled in all the api info and we both have a valid ESTA but i still keep getting the same message

and you are selecting the option that says you are an ESTA holder

Can this happen when you have been selected for secondary security checking? Happened to me once on a VS1 flight - OLCI completed but it wouldn't email me the boarding pass, but claimed it was a technical issue.

At bag drop I was told this is so they have to issue the pass there.