why can I not load photos from my Pentax K40 camera

Are you shooting RAW? The RAW format of the Pentax K40 is not on the list of supported cameras, see: Digital camera RAW formats supported by iOS 17, iPadOS 17, macOS Sonoma and visionOS – Apple Support (UK)

As a test, change the settings on the camera to use a different format, for example shoot TIFF, or whatever is supported on your camera and see, if Photos will then import the photos.

Where are you trying to import to? The Photos app or to a folder? Are you using the Image Capture app or something from Pentax?

I find it easier to just remove the SD card (K5 usually RAW) and read it directly via USB instead of connecting the camera.. Then you can select what you want and drag that to the destination. You should be able to import both .PEF and .JPG.

Obviously if the poster is shooting other than RAW, then it is a different issue.

I cannot find a reference to a K-40. Perhaps in some other world markets. The older K-30 and the K-50 (in Apple list) both claim RAW.

The poster needs to provide more specifics.