Running Tasks Gives "The thread is no longer running"

We are using Kentico 9.0 and are trying to rebuild some indexes. I check the tasks tab on the admin area under the Smart Search app but found the tasks have not executed. When I click the @Process Tasks@ button and click the @Task processor is running. Watch progress here@ link I get this message:The thread is no longer runningWe are using virtual storage on Amazon S3. I checked and deleted any lock files there. There are subdirectories for each smart search index.I appreciate any ideas.