Motion Graphics are green

Hi there,

Please also try disabling hardware accelerated decoding & encoding under Edit > Preferences > Media & check if it's restoring the preview.
Note: You would need to restart Premiere Pro after making these changes.

Thanks,

Sumeet

Delete the Media Cache and Media Cache files:
https://community.adobe.com/t5/premiere-pro/faq-how-to-clear-your-media-cache-in-30-seconds-in-premiere-pro-2020/m-p/11017257/thread-id/260446?page=1

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/8236158?page=1

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 NVIDIA, do a clean installation of the latest Studio Driver (NOT the Game Driver)

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

It looks like something is wrong with the background, and that depends on the template and the options provided with it. Does it require any third-party plugins? Is it compatible with your Pr version? Do you have the option to replace the background and you didn't do that?...
Also, posting a screenshot of the template's options in the essential graphics panel would be useful.