Can't install tensorflow with pip or anaconda
You mentioned Anaconda. Do you run your python through there?
If so check in Anaconda Navigator --> Environments, if your current environment have got tensorflow installed. 
If not, install tensorflow and run from that environment. 
Should work.
Does anyone know how to properly install tensorflow on Windows?
I'm currently using Python 3.7 (also tried with 3.6) and every time I get the same "Could not find a version that satisfies the requirement tensorflow-gpu (from versions: )
No matching distribution found for tensorflow-gpu" error
I tried installing using pip and anaconda, both don't work for me.

Found a solution, seems like Tensorflow doesn't support versions of python after 3.6.4. This is the version I'm currently using and it works.