ssrs subscription can not be created

Hello,
The ssrs report runs fine.
It has several parameters
example: 
param1, populates param2.
Param1 is only one item to be selected
param2 is multi-select

I have a subscription to send emails for the report.
subscription works fine if param2 has less than around 1000 items
subscription can not be set when the param2 has more than around 1000 items and the error I get while creating a subscription for this scenario is: Operation is not valid due to the current state of the object. 

Any suggestions how to solve this subscription please?
Thank you