pyRevit Is Installed But Does Not Load

Open a command prompt and run pyrevit attached
Take a look the ==> Attachments section. It should look similar to this. It should show that master is attached to all your installed Revit versions. The report looks similar to this:
```
==> Attachments
master | Product: "2020.1 Update" | Engine: IPY2712 (2712) | Path: "....."
master | Product: "2019.2.2 Hotfix" | Engine: IPY2712 (2712) | Path: "....."
```

If nothing is listed then run pyrevit clones and check to make sure master is listed as the installed clone

==> Registered Clones (full git repos)
==> Registered Clones (deployed from archive/image)
master | Deploy: "basepublic" | Version: "4.8.5" | Path: "......"

If it is listed, then run pyrevit attach master default --installed and check again to make sure it is attached.
If it is not listed, then find the installed pyRevit path (default is %APPDATA%/pyRevit-Master ) and manually register the master clone by running pyrevit clones add master <installed path>. Then check pyrevit clones to make sure it is registered. Now you can attach it using the command in previous step.

See an example of this fix here

Installation still not working after serveral trys · Issue #1075 · pyrevitlabs/pyRevit

Error dynamically compiling pyRevit runtime

What seems to work in most cases:

Uninstall pyRevit
Delete C:\ProgramData and \%AppData%\ pyRevit folders
Move all Revit addins to a temporary location. Usual addins locations include:
1. %AppData%\Autodesk\Revit\Addins\<year>
2. %AppData%\Autodesk\ApplicationPlugins
3. %ProgramData%\Autodesk\Revit\Addins\<year>
4. %ProgramData%\Autodesk\ApplicationPlugins
[Reboot computer]
Reinstall pyRevit
Started each version of Revit confirming pyRevit successfully compiled at startup.
Moved all Revit addins that were moved in step 3 back to their original location.
1. you may want to add them one at a time and start a revit session everytime to figure out which ones are causing the issue.