In order to get trend net switch to work again, I first shut down both computers. Unplug both usb cables from computers, turn off monitor until flashing light goes out on switch.
Then reinstall all cables, turn on monitor and boot machines one at a time.
I have to do this every so often just to keep the switch working.

Computers & Internet - Trendware - TK-207K 2-port USB KVM Switch