You're looking at StableBuild's Deleted PyPI mirror - where we index all deleted packages from the Python package registry.

appdynamics-proxysupport-linux-x64
1.8.0.51

This version was deleted from PyPI around 2023-11-01. Installing fails with:
$ pip3 install appdynamics-proxysupport-linux-x64==1.8.0.51 ERROR: Could not find a version that satisfies the requirement appdynamics-proxysupport-linux-x64==1.8.0.51
View other deleted versions of appdynamics-proxysupport-linux-x64

Install through StableBuild

You can install this package from StableBuild's PyPI snapshots from before the version was deleted:
pip3 install \ -i https://YOUR_API_KEY.pypimirror.stablebuild.com/2023-10-31/ \ appdynamics-proxysupport-linux-x64==1.8.0.51
Sign up for StableBuild to get an API key (it's free and takes <60 seconds!)

Or, download files manually

And install manually via pip:
appdynamics_proxysupport_linux_x64-1.8.0.51-py2-none-any.whl (39.6MB)
appdynamics_proxysupport_linux_x64-1.8.0.51-py2.py3-none-any.whl (39.6MB)