Text formatting not visible in editing mode but is in reading mode

Help
1

What I’m trying to do

I’d like help in understanding why my text formatting (i.e. selecting text, applying bold and a heading size) isn’t visible in the editing mode, but it is reflected when I click the reading mode?

Things I have tried

I have searched for existing forum posts and can’t see a solution, so keen to understand what is causing this.

2

Can you share a screenshot and some example text, in a code block, where you see the issue? It might be easier for folks to spot something with an example.