Product: Programmable SMS
ERROR - 35115
Scheduling does not support this timestamp
OptimizeStartAt time must be between 3600 seconds and 604800 seconds in the future, inclusive.
Scheduler currently doesn't support scheduling messages for an optimized time less that 1 hour from now, or more than 7 days in the future.
Verify that the OptimizeStartAt parameter is using "[YYYY]-[MM]-[DD]T[HH]:[MM]:[SS]Z" format ( in UTC ).
Check if OptimizeStartAt parameter exceeds at least 1 hour (3600 seconds) from the time of request.