Thank you for your message.
Please, check that:
1. You didn't accidentally pressed the Full Control / View toggle icon (it's the first icon on the toolbar in the Full Control mode). When it is pressed, you are in Full Control mode. When it isn't, you are in View only mode with mouse and keyboard not working.
2. Provided that #1 is not the case, does this happen all the time or do the keys work after you re-initiate the remote session?