Hi @Yulia, welcome to community!
I am a bit lost for context here. Could you kindly give a bit more information, idealing with a reproducable example? (here's a link with a bit of info on why and how FAQ: What's a reproducible example (`reprex`) and how do I do one?)
If I were to take a wild guess, you're working with a shiny app and you use a function outside of a reactive call. But that's just wild, downright-irresponsible speculation. I'm looking forward to finding out.