Google applications like Docs or Sheets have a number of pre-made templates that help you easily create content quickly. You can also create your own templates and upload them to the Template Gallery. However, sometimes it may happen that the template is hidden in Docs, Sheets, from which you cannot select the content template. Below are instructions for fixing hidden template errors in Google Docs.
Turn on Show Recent Templates on Docs
You might not be able to view templates in Google Docs or Sheets if you accidentally turn off Show recent templates.
Step 1:
You click 3 dashes icon then select Setting in the displayed list.
Step 2:
Switch to the new interface, select it item Show recent samples on the screen to display the Google Docs Template Gallery again.
Restore original files
Google allows you to use custom templates by uploading files to Google Docs. However a shortcut of the template file is created instead of a copy. If you move the original file, the shortcut will also disappear so that might be why you don't see your custom templates.
To fix this, you need to restore the original template to the previous location where you uploaded it to Google Docs.
Check file permissions
If you've shared your custom template file with others and given them editing permission, they can remove the template from the library. This doesn't mean the template will be removed, but it will no longer be visible in the gallery. Consider checking permissions and removing editing permissions for others if you don't want them to delete them again.