unable to add or remove users to the scheduled report : Error Limit Exceeded You or your organization has exceeded the maximum limit

@Anjana, take a look at this help doc.  According to this, you have 3 options

1. You can reach out to your Account Executive about purchasing more scheduled reports.  
2. Carefully select the reports you want to schedule and try to find the correct balance between frequency and number of schedules (sending the report more often will impact the maximum number of reports sent per hour, while scheduling a similar report multiple times might affect the maximum number of scheduled reports per organization). 
3. Unschedule from any reports that have no future run.