Translation:The plate is lying in front of the cup.
I know this has come up earlier. Keeping lie from lay is evidently tricky even for the native English speaker. The way I read the paragraphs; lies is the correct action for the plate.
Start copy paste from my Oxford advanced learner's dictionary: Lay -to put sb/sth in a particular position, especially when it is done gently or carefully
Some speakers confuse this sense of lay with lie, especially in the present and progressive tenses. However, lay has an object and lie does not: Correct: She was lying on the beach. Wrong: She was laying on the beach. Correct: Why don't you lie on the bed? Wrong: Why don't you lay on the bed?
In the past tenses laid (from lay) is often wrongly used for lay or lain (from lie): Correct: She had lain there all night. Wrong: She had laid there all night.
Lie - 1 (of a person or an animal) to be or put yourself in a flat or horizontal position so that you are not standing or sitting. 2 (of a thing) to be or remain in a flat position on a surface
End copy paste
(And I upvoted you to compensate;-) Based on the way I (usually) use my ups and downs I understand your miffiness completely! I downvote stuff that are wrong or obscene, and I upvote good replies... The rest I leave be. You should be allowed to ask, how else will we learn!)
Probably you were not downvoted (I didn't do it by the way.) for asking the question but for the assertion that they meant the same thing which was wrong.
Next time you might say "I thought they were the same thing." if you were unsure as "lays" would be interpreted as the past tense unless someone was mentioned who was currently putting the plate there as plate would need to be the object. "She lays the plate in front of the cup." or "She is laying the plate in front of the cup." I know it seems strange to use "lie" and "lying" because we know the plate did not lie itself down, but it is there now and is not moving so we can say that it "lies" there or "is lying" there. We might more commonly say that it "is" there, but in Norwegian they more commonly give its orientation by using their word for either "lies" or "is lying or "stands" or "is standing". "The umbrella is standing in the corner." simply gives more information and lets you know that it has not fallen down.
In Norwegian, we like being more specific in our choice of "position verbs". So, where it in English would sound natural to use the general "is", it's often more common to use "ligger" or "står" in Norwegian than it is to use the more general "er".
The literal translation of "ligger" is "lies", but the most natural approximation will often be "is".