Movie Posters on MP4 files are disappeared

Dear all friends,
Nice to meet you. Greetings from Myanmar.
I have a problem.
I am using Mp3tag on my PC (Window 10).
I make photo covers on movie files using Mp3tag. It is easy to use.
When I have updated my PC's Window 10 to lastest version.
And I have found that photo covers on my movie files have been disappeared.
Please help me. How to fix it.

First of all I would like to know where the pictures disappeared. Is it the Windows Explorer?
Have you modified any explorer settings so that only the icons are shown?
You could consult internet pages that deal with windows settings like this external one:

Anyway, you could check your MP4 files and see if they have embedded pictures.
Load them into MP3tag,
apply the following filter:
%_covers% PRESENT
and to check the opposite (no embedded pictures)
%_covers% MISSING

If there are embedded pictures, you could export them to the file folder.jpg.
Use the corresponding action for that:

For files where there is no embedded picture and windows does not show any pictures I am afraid that you have to look for them again.