Hello, [ERROR: Can’t determine which item to use]

Hello,

I have this ERROR, and i can’t know the solution, i have a Spreadsheet node that read the excel file with the emails that i want to send them, but sometimes work clearly and done, and sometimes stop with this error and i don’t know why,

if anyone know the solution Please help me

I solved it—I used a Switch node that the same output make two different department names because I set the condition to “contains” to the department.