Cannot use any of the fonts in Acrobat Pro 2020

Hi there,

Until a couple of weeks back I could choose any font from the extensive list when building documents, posters, etc.  Now I cannot get any of them - especially when I'm editing text in a pdf already created.  Acrobat is permanently 'stuck' on Helvetica and whenever I choose another font it ignores the request and defaults back to Helvetica.  Does anyone know how to fix this, please?