Can't select multiple files via shift key or command key-wassup?

That says it all. I can no longer depend on holding down the shift key to select a list of files or holding down the cmd key to select multiple separate files, like for getting rid of trash. That means that I have to go from file to file, individually selecting and disposing of (or moving, or collecting in a folder) each file separately. It's the 1980's all over again! Any solutions? PS-I'm on an M1 Mini running Sonoma 14.1.1.