Impossible to know anything without any info on what properties you are trying to copy & paste from where to where along of course with the usual niceties like system info, details about your project and so on. Since your user name implies that you may be from an Arabian country, using a different language version or having a layer named in a way that is not compatible with expressions could be the issue just as well. You definitely have to provide much more details before anyone can even guess.
Hey, bud, I'm not Arabian and I think nationality is not important for solving the issue. please read carefully the problem I shared and if you have a bit of time, you can make a simple project and make a test.
Again, you have not provided any info such as what properties you are copying from and to or your system info, so we can't really help you. As they say the devil's in the details and while this error seems to crop up a lot lately, it is most definitely not consistent and depends on the context.