Good evening
I installed Neon a few days ago and I have a problem with discover app center
there is no categories in the left side
how i can fix it plz

I have just checked my system and 'Discover' is the same as yours. I had not noticed before as I generally use 'synaptic' to install software.

Discover showed the 'apps' bit when I installed using the iso snapshot dated the 08112017 so it must be a bug that has crept in with th subsuquent updates. This can be reported at:

https://bugs.kde.org/

I am experiencing the same issue on KDE Neon 5.11. The software center displays all the categories correctly after installation, however, the first update after the installation seems to break Discover. I haven't found a solution for this as yet.

There were some qt updates this morning - which have fixed this issue.