Hi Slava, I think you are facing this issue because you didn't initialized the dictionary. When you insert AddToDictionary activity to the sequence and create a dictionary variable you have to initialize it with newDictionary() method. You can initialize a dictionary in 2 ways:
1. Use Assign activity to assign dict variable to newDictionary(key_variable_type, value_variable_type):
dict = newDictionary(Of String, String)
2. Initialize the dictionary while creating the variable by providing default value as newDictionary(Of String, String)
To understand better, checkout this thread: https://www.edureka.co/community/41092/can-i-create-dictionary-in-uipath-studio-and-add-items-to-it?show=41092#q41092