Hello @Mahesh Venkatashamappa , please ensure you have a valid Microsoft 365 or Exchange Online license assigned for the target user. If you do and the problem persist, please come back with new response/debugging information.
Let us know if this answer was helpful to you or if you need additional assistance. If it was helpful, please remember to accept it and complete the quality survey so that others in the community with similar questions can more easily find a rated solution.