In proactive’s scenarios, the conversation Id for channels change when the user answers your message, it’s like a new session, we do this type of features using the channel data, but this solution is only for small data, you also have the option of creating a persistent session using the same table storage that the bot framework is using to save the dialog context, in this solution you can create another table to store your data serialized, and the final one is a persistent session using a distributed cache like Redis, but this type of services are expensive, so you have to analyze which type of solution is the right one for your solution, but as a start, you should try with the Channel Data property and if it works, you can analyze another approach
I hope I have been helpful