I'm experiencing the same issue. Any suggestions?

What I've noticed is that if the size of the data in ActivityAttributes exceeds 4K I receive this error. The docs state that the size of ContentState updates cannot exceed 4K but I haven't seen anything about limitations for the initial ActivityAttributes sent when starting an Activity. I'm not sure if this is intended behavior or just a bug in the beta? Since the Live Activity cannot perform network operations in its "sandbox" it seems very odd that you're only able to send a very small amount of data when starting an Activity.