If the "Subfolders" is selected in Filters(12) field, with or without a mask, the search can take a while. That's OK and understandable. But there is ALMOST NO FEEDBACK to the user that anything is going on! You may be led to think there is no file/folder matching the mask!
If you look very carefully, there is a faint indication at the bottom right of the screen that a search is been done, but it is coverd by the banner "Bulk Rename Utility is free for personal non/commercial......"
My suggestion is simply either one of
1) Make the banner clickable to make it disappear after reading it.
2) Make the banner shorter so at the right of it the search is displayed.
3) Display symbol (a swirling circle, a flashing text, or something dynamic that catches your eye
that indicates the search is still on.
Thanks for a remarkable program!