So, I wanted to check how my engine looks like in Cycles but then I got some issue with initialization and Cycles viewport preview is canceled.
How to fix that?
How long does it take to initialize a final render, if it starts at all? Does it help utilizing simplify function, i.e. to limit excessive subdivs? Does the binary method help? Hide half, then other half, then a quarter etc - maybe there is a single object causing issues? Issue with the instancing groups? Can you append parts of it to new project and it works there?
I guess I have nothing but questions, huh? 
TL;dr: 3D Viewport Rendered Preview POSSIBLY PAUSED
This looks suspiciously similar to when the 3d Viewport Preview is paused. However I don’t see the pause button in your gif. Try switching to Eevee and switching back, or changing Cycles settings (GPU/CPU/Stan/Exp), and/or going into edit mode and/or Wireframe mode and switching back, AND/OR going into Local Perspective and switching back and Maybe the pause button on the top right hand side (Next to the Rendered/Viewport Shading drop down) will show up. Then unpause the render.
Sorry for the weird steps. But when the viewport does not refresh/update, I go into wireframe or take any of the above steps and it updates/gets fixed. Known issue. With certain features, you have to check/uncheck a random box so the viewport refreshes.
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You’re right dude, I forgot that I paused the rendering process, hahah lol :v
thanks dude