It might be multiple @ is causing the issue.
FYI:
#PBS -W stagein = <execution_path>@:<storage_path>
#PBS -W stageout = <execution_path>@:<storage_path>
stagein: location of input files ( copy input files to the execution directory or job directory)
stageout: location of output files (copy results from job directory or execution directory back to you intended location )
execution_path: execution directory on the compute node
storage_path: filename on host hostname
The ‘@’ character separates execution path specification from storage path specification
@ character is just a separator, it does not represent username@hostname kind of specification