DM,
Hello. welcome to fishing.
There are lot's of different reasons why a bite can be on or off but usually it is that the fish have moved on, the tide isn't ready yet or they are eating something different than what you just offered. Bass can be real finicky and, when they are inshore, are easily spooked. If the spot is super busy they can get rattled by the tons of plugs and assorted efforts hitting the water and make themselves scarce.
Was the tide setting up the same way when you returned the second time ? Many times a certain spot is very tide reliant.
Regardless, they are many different reasons and most of it can be learned through some good literature that is available. Even the crustiest, old salt has a few of these books on his or her shelf.
Check your local Tackle shop or check online. Daignault, Tabory, etc. are some of the names to look for.
One of my hardest lessons to accept was that it would be hard for me to catch a fish EVERY time I went.
Good luck and enjoy the holiday.