Hi.

Seems you lowered the opacity values somewhere.
Any chance you lovered a layer's opacity?

Select your object.

Look into the bottom left corner of the Inkscape window, into the field that says 'O' for opacity (or different letter in your language). It must be at 100% for full opacity.
Look at the field for the fill color in the bottom left corner. Is there a checkerboard pattern visible? Click on the fill color field. In the fill and stroke dialog, set the value for Alpha to maximum.

Open the layers dialog (Layer > Layers). Set the opacity value for all layers to 100%.

This tutorial explains how to fix transparency or opacity problems: https://forum.inkscapecommunity.com/ind ... article=18