I am facing the same issue. No version of the faiss library is being recognized as present in the environment I am running (installed through conda). I did solve this problem before, but I remember it being a pain; I built the library from source but had to deal with many issues along the way.
Edit:
I was just able to get it to be recognised.
Solution:
if you are able to import the library ( from terminal start python):
python
import faiss
print(faiss)


/home/akinwilson/miniconda3/envs/envRag/lib/python3.7/site-packages/faiss/init.py


take the path;
/home/akinwilson/miniconda3/envs/envRag/lib/python3.7/site-packages/faiss
then in your bashrc file:
nano ~/.bashrc
add this line to the end of the file:
export PYTHONPATH=$HOME/miniconda3/lib/python3.8/site-packages/faiss
Note that I have changed the home directory to a variable.
save it.
Then finally, set the bashrc file as source again to reload the paths;
source ~/.bashrc
Restart any virtual environment and everything should work fine.