can't cut the mustard
1. slang Is unable to work or operate in a satisfactory manner. I need a new worker from the temp agency—the one you sent over keeps mixing up orders and just can't cut the mustard. This toaster can't cut the mustard anymore. No matter what setting you choose, your toast comes out charred!
2. slang Is unable to work or act with energy and enthusiasm. That guy looks like he's 110 years old—I'm sure he can't cut the mustard stocking shelves all day!