Here's the standard shinyapps.io deployment troubleshooting guide I'd encourage you to consult,
https://docs.rstudio.com/shinyapps.io/Troubleshooting.html
And then to parret andresrcs, additional information about the error is helpful in diagnosing the issue. The guide he linked to will help you create a post here optimized to get help.
Often those shiny logs and tracebacks are useful to others trying to help out. Even if you have trouble reading them, reporting them here might help