It’s going to be difficult for anybody to help without some more information, and ideally a reproducible example of your problem. Shiny issues can be more challenging to debug than regular R code, and creating a good Shiny reproducible example is a bit more involved, but we have a guide that covers both topics:
I recommend reading through that and then (assuming you haven’t debugged the problem yourself!) updating your question with as close as you can get to a reproducible example (doesn’t have to be perfect!).