What do you consider a sign of fermentation anyway?
, and by visible signs we don't necessarily mean a bubbling airlock.
It IS a sticky at the top of the beginners forum for a reason, afterall.
As already stated in the linked sticky, Fermentation often can take up to three days to start. And by visible signs they do NOT mean airlock bubbling.
After 72 hours take a hydro reading....until then relax.