PETScVector could not be imported - openmdao

Question

I am trying to use MPI in OpenMDAO. I get the following error. It seems to come from this. But I don't understand what is causing this error or how to fix it.
Traceback (most recent call last):
File "/home/users/RBMDO/Power_Subsystem.py", line 494, in <module>
prob.setup()
File "/home/users/.conda/envs/my-fastenv/lib/python3.8/site-packages/openmdao/core/problem.py", line 874, in setup
raise ValueError(self.msginfo +
ValueError: Problem: Attempting to run in parallel under MPI but PETScVector could not be imported.
Traceback (most recent call last):
File "/home/users/RBMDO/Power_Subsystem.py", line 494, in <module>
prob.setup()
File "/home/users/.conda/envs/my-fastenv/lib/python3.8/site-packages/openmdao/core/problem.py", line 874, in setup
raise ValueError(self.msginfo +
ValueError: Problem: Attempting to run in parallel under MPI but PETScVector could not be imported.
Traceback (most recent call last):
File "/home/users/RBMDO/Power_Subsystem.py", line 494, in <module>
prob.setup()
File "/home/users/.conda/envs/my-fastenv/lib/python3.8/site-packages/openmdao/core/problem.py", line 874, in setup
raise ValueError(self.msginfo +
ValueError: Problem: Attempting to run in parallel under MPI but PETScVector could not be imported.
Traceback (most recent call last):
File "/home/users/rpandi/RBMDO/Power_Subsystem.py", line 494, in <module>
prob.setup()
File "/home/users/.conda/envs/my-fastenv/lib/python3.8/site-packages/openmdao/core/problem.py", line 874, in setup
raise ValueError(self.msginfo +
ValueError: Problem: Attempting to run in parallel under MPI but PETScVector could not be imported.
--------------------------------------------------------------------------
Primary job terminated normally, but 1 process returned
a non-zero exit code. Per user-direction, the job has been aborted.
--------------------------------------------------------------------------
--------------------------------------------------------------------------
mpirun detected that one or more processes exited with non-zero status, thus causing
the job to be terminated. The first process to do so was:
I verified MPI and petsc are working in my environment, I ran the small petsc4py script given here. It runs successfully and gives the expected result.
For completeness, I am running a MINLP optimization with AMIEGO and my job script is below.
#SBATCH -N 1
#SBATCH --ntasks-per-node=4
#SBATCH -c 1
#SBATCH -p batch
#SBATCH -C skylake
print_error_and_exit() { echo "***ERROR*** $*"; exit 1; }
module purge || print_error_and_exit "No 'module' command"
module load lang/Anaconda3/2020.02
module load mpi/OpenMPI/3.1.4-GCC-8.3.0
conda activate my-fastenv
mpirun -n $SLURM_NTASKS python /RBMDO/Power_Subsystem.py
Any idea on what might be causing this error ?