Before posting to the forum here, you should carefully read this post Please Read This First: Guidelines and Suggestions for posting LAMMPS questions
Creating a topic where there is no question, no explanation and just some quoted error message and some input file content that is difficult to read since it was not properly quoted, is not likely to get an answer. Also, it is very bad practice to post the same question twice.
The error message you quote is rather self explanatory. Apparently the group that you try to apply the velocity command on contains no atoms. That is something that you can easily debug on your own.