Hi Aldrey,
From the image (that you have attached) , I can say that , the desired object is not found when test is running.
Could you please remap it and try to run it ?
This error also occurs when there is change in object hierarchy. I would also recommend you to have a look at "Extended Find" option. This might resolve your problem.
Also , to add further , please try to give unique properties whilst mapping a object , It might be the case the , the object has same properties as other and it creates problem while identifying the particular object.
I hope this has been of some help.