Non-breaking spaces not visible

Hello, 

I have a problem, which occurred after my SDL Studio 2019 was reset. When I insert non-breaking space using Ctrl + Shift + space, the non-breaking space can be normally inserted and is visible. However, if I want to find all combination of words which require non-breaking space and replace them all by a non-breaking space, this does not work, as the non-breaking spaces are not visible. This really affects my work since in Slovak language, these are quite important. 

I would very much appreciate some help.

Thank you.

Lenka