Hi @maciej_glowacki2EU2B,
I hope you're doing well. Thank you for the picture, that was key in figuring it out. You have an unusual board shape and I fully believe that it's area is less than 80cm^2. With that said the area limitation is based on a rectangular envelope where the bottom left corner is at 0 0. The top right corner is at the copper object that is the furthest away in the X and Y axes. You have some components already placed at around 4inches in the X dimension which means that the furthest any parts could be placed in the Y axis is around 3inches, so the move you are trying to perform wont work because you are trying to place it near 5inches in the Y direction.
So the key thing here is to realize that it's not measuring the outline of the Dimension layer, but using the extents of copper in the design to form a rectangular envelope and calculating the area of that do determine how far new moves are allowed to go.
I know it's a lot so if you have any questions on the above. Please let me know.
Best Regards,

Jorge Garcia
Product Support Specialist for Fusion 360 and EAGLE
Kudos are much appreciated if the information I have shared is helpful to you and/or others.
Did this resolve your issue? Please accept it "As a Solution" so others may benefit from it.