You may want to check the main VeriFLY thread, but the short version is that after VeriFLY sends over an OK to BA, BA isn't always that quick to clear the ADOC flag to release the OLCI. Sometimes after time it clears, sometimes it's automatic, sometimes it doesn't clear, so you have to go to a check-in desk. Having done VeriFLY means the agent doesn't need to check your paperwork or scan anything so it saves time in that respect. There are other reasons why OLCI doesn't work - see upthread, but SSSS is the well known factor.