Personalized templates not saving in Presentation Editor

[SophieTamara]

I am trying to create personalized slide mask in the Presentation Editor, but it won't save my changes.

For example:

If I change the font from Arial to Avenir and add a blue background to a slide in the slide mask editor:

Then I go back to normal view, I add a new slide choosing from the list of slide templates, but the newly colored background slide template is not there (it shows up sometimes later, but not always). I create a new slide by selecting the Title slide template and sometimes it will show up blue, sometimes not, however, it never shows the new Avenir font.

Although, when I go back in the slide mask editor, the blue background is still there as well as the new Avenir font.

Then, when I save and close the presentation, and reopen it, the changes are gone in the slide mask editor.

This is for a .otp file.

I tried with .odp (same issue even worse).

I also tried with a .pptx file for which the issue is a little different:
Once the slide mask edited, the blue background slide shows up in the list of slide templates in the normal view, but it doesn't keep the new Avenir font on it, it creates a slide with the Arial font instead; and when I close and reopen the file, the slide mask is still there with the blue background and the Avenir font, but the font still doesn't show up when selecting the slide in the normal view.