After following the process
If you are using your report class for your report then don’t convert the report in content.Then this problem will not arise again.
Right click on your solution or crystal report folder. Go to Open Folder In File Explorer.
Select your report. You have to choose only the rpt file not the cs file of your report.
Copy the report & save it Desktop or another place.
Now Delete the crystal report, If you are using source controller also delete from it.
Now add the report as existing file where you save the rpt file, It will automatically generate it’s cs file.
Now build & run your solution.