It is very important to keep the 'congrats' or 'survey completed' screen open for at least 10 minutes or so. Shrinking it and opening my browser again to check my account page or whatever has not interfered with crediting for me. If the survey does credit, the approval invariably shows up on the FC toolbar scroll before it credits on the account page.
Of course, there are glitches and the crediting system by the sponsors of the daily surveys certainly needs some improvement. There is really nothing FC can do to help with that though. All FC can do is offer tips to give you the best shot at having the offers credit.
By following the tips offered by FC and members in the forum, I have improved my percentage of survey successes markedly without having to take excessive time with them. Yeah, some surveys are long and tedious, then don't even credit, but others do. You have to decide for yourself whether the dailies are worth your time and effort. My best advice is to read the suggestions of other members very carefully. Some members do quite well with these, and I count myself among them. The approvals apply to the $15 in offers needed for cashing out after all.