Jeanne19 :
I do not have another keyboard, the connector is not ask USB port, it's round and color coded
You might send the model of the keyboard. It sounds like you have perhaps an older keyboard since your connection, that round plug, is probably a "PS/2" connector. Most contemporary keyboards use a "USB" port- that looks like a little rectangular plug the fits into a like female port hole.
Sometimes a keyboard comes with some special software from the maker (Logitech) called a driver and special configuration application(s). Sometimes that software gets corrupted and has to be reloaded. You might go to Logitech's support page and with the model number see if they have an updated driver/configuration software package you can download and install on your computer.
You also might look into the end of the PS/2 (the round plug) and see if the pins are straight and haven't bent which could cause the keyboard to not connect properly. If so take a very thin needle nose pliers and carefully bend them back straight, I have used the bottom part of a retractable pen and slipped the pen over the pin to straighten it out--of course you need to remove the ink cartridge first.
With Respect,
DBellas