OK, i'm returning to this thread and backing up Philbo's original report.
Although my previous suggestions worked for him on that occassion, I have since tried to replicate my solution and now it no longer works.
Short of creating a bare bones project with just a widget with a text field and custom font, nothing I attempt to make the font now show works!
This issue is further compounded by the fact that font size in text fields isn't updating either (an issue also mentioned on the Discord).
Text Labels work immediately, both font size and font, but for some reason ,text fields, even if read only, refuse to acknowledge a change to either font or size in-game.
I am going to include a project with widgets and font for you to look at Justin.
Project Zip:
Here is a project that has three widgets with a text field that, while set to different sizes and font in editor, do not show in game.
I even have one appear immediately on startup, but it doesn't show the font settings.