Blue tit nest box activity

Good morning,

we have a pair of Blue Tits who have shown a large amount of interest in one of our boxes. They have been constantly in and out, bringing various items back with them for nest building. However we’ve seen no more activity for about five days from either bird?! Is something wrong or are we just looking out at the wrong time?? We don’t have a camera box so can’t see what’s going on inside.

Any suggestions/advise would be appreciated. 

Thank you in advance.