I was able to resolve this and am documenting for others. For background, my app is huge and in order to make it scale it is broken down into many subcomponents that are sourced in. For those familiar with Flask, it's like the concept of Blueprints to grow an app easily and manage code.
One piece of code that is grabbed in my app is the "libPack.R" which is all of the packages that are needed..
Locally (and on shiny server on premises), I just use an lapply and add to the package list as follows:
#Packages <- c("data.table", "plyr", "dplyr", "sqldf", "lattice", "latticeExtra", "stringr", "statmod", "gridExtra", "readr", "R.methodsS3", "Matrix", "nlme", "foreach", "doParallel", "RODBC", "ggplot2", "readxl", "corrplot")
#lapply(Packages, library, character.only = TRUE)
For some reason, this does not work when deployed at apps.io. Instead, I had to explicitly call each library as follows:
library(data.table)
library(lattice)
library(gridExtra)
library(latticeExtra)
library(plyr)
Hope this is helpful to others as they build and deploy.