I recently updated to Version 15.4 Build 3089 and everything was fine. Then a few days ago, I updated Windows to 24H2 Build 26100.3915. Before this, using Ctrl-C and Ctrl-V did a File Explorer file copy, showing the file copy progress window. Since this Windows update, the copy still happens, but no copy progress window is shown. Doing a copy using File Explorer does show the progress window, but no window appears using Multi Commander.
FYI, I use Ctrl-C and Ctrl-V since it's significantly faster than using Multi-Commander Copy.