When I try over terminal i get this - ./MLV.App.v1.11.Linux.x86_64.AppImage: error while loading shared libraries: libnsl.so.1: cannot open shared object file: No such file or directory
The MLVapp appimage for Linux is sort of messy. It contains two binaries that are different, and one of them commonly gives errors similar to the one you mentioned, although I suspect that the problem might also involve Fedora's removal of the library in question, to which @masc linked.
Try extracting the appimage (which creates the "squashfs-root/" directory containing all files), and then run the MLVapp binary that usually doesn't give the dependency errors:
$ ./MLV.App.v1.11.Linux.x86_64.AppImage --appimage-extract
$ ./squashfs-root/usr/bin/mlvapp
If you still get the same error on the missing library, try copying the library from where it resides on your Fedora install into the newly extracted lib directory:
$ cp -ivp /path/to/your/fedora/library squashfs-root/usr/lib/
Now, try running the MLVapp binary again:
$ ./squashfs-root/usr/bin/mlvapp
I have installed libnsl, but nothing has changed
If the above steps don't work, make sure that you have the specified version of the needed library(s). If you are using another version of the library, install the needed version and repeat the above steps.
If none of these steps work, you could also try the same commands above with the usually problematic MLVapp binary and see what happens. To start that binary, do this:
$ ./squashfs-root/mlvapp