Can't paste, or move anything in my Timeline

I have a full string out of hours of footage.  When I cut several clips from the start of the sequence using Command-X, and then try to paste them at the end of the sequence, the clips are removed, but nothing is pasted.  I've tried Command-V, Shift-V, and when I look at the pulldown menu from the menu bar, "paste" isn't even highlighted as an option.

I also don't seem to be able to drag anything in the timeline, either horizontally, or onto other layers.  I can't drag from the source window to the timeline, and the Insert and Overwrite functions aren't working either - either from keyboard commands, or interface buttons.

I'm running Premiere 24.3, running Mac OS Sonoma, 14.1.1 on a Mac Studio M2.

Please help!