One video clip is frozen in my project

And if that doesn't work...

Try resetting the preferences:
https://community.adobe.com/t5/premiere-pro/faq-how-to-reset-trash-preferences-in-premiere-pro/td-p/...

If that doesn't work, try resetting the Workspaces:
Reset a workspace
Reset the current workspace to return to its original, saved layout of panels.
1. Do one of the following:
• Click the Workspace menu icon and select Reset to Saved Layout.
• Choose Window > Workspace > Reset to Saved Layout.
from here:
https://helpx.adobe.com/premiere-pro/using/workspaces.html

If that doesn't work, try Preferences > Audio Hardware and set Input to None.

If that doesn’t work, try updating or rolling back your graphics driver directly from the video card manufacturer’s site.

If that doesn't work, try creating a new project and import the old one into it.

Try a new sequence. Select the New button at the bottom of the project window, and create a sequence. Drop that clip into the sequence (from the project) and see if it plays.

It should be in the project somewhere. Find it and double-click it to open it.

Try this:

• Start PP from it's normal desktop icon (IE: don't open from a project file link).
• Close the Open/Home screen (and you will be in PP without a project open).
• Go into Edit/Preferences/Media Cache (Mac users adjust menu name)
• Then Press: Remove Media Cache Files: and Delete...
• Select: Delete all media cache files from the system and OK
• Close PP - It will create any needed cache files on the fly as you edit.