Low resolution/pixelated image

You may have disabled the display of higher quality images...

1. Click Tools>Viewer Options to open the Options panel; the Image tab is displayed.
2. Is the Disable higher qualities box checked under Movement Resolution? If it is, un-check Disable higher qualities.
3. Zoom out with the mouse wheel, then zoom in again.

See an example

BEFORE ↓

AFTER ↓

Do you only see lower quality while panning or focusing?

1. Click Tools>Viewer Options to display the Image tab in the Options panel.
2. Under Movement Resolution, move the slider closer to Quality to improve resolution when panning and focusing .

Image compression on the original image and the compression factor used when creating the virtual slide both affect what you see.