Product: Programmable SMS
ERROR - 35116
Scheduling does not support this timestamp
OptimizeEndAt time must exceed OptimizeStartAt and be at within 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 OptimizeEndAt parameter is using "[YYYY]-[MM]-[DD]T[HH]:[MM]:[SS]Z" format (in UTC).
Check if OptimizeEndAt parameter exceeds (is after) the OptimizeStartAt parameter.