I'm not sure why I hadn't thought to try that through Tv itself I don't know if I could have solved it without going to the remote machine, but hopefully that is helpful to anyone else with this problem. What ended up resolving the issue was pressing ctrl-alt-del on the remote machine to bring up the help/lock screen, and that was it! Just from that, I regained full control both locally and remotely.

This program is operational on Windows XP all the way to the Windows 11 operating system version.

Turns out, I had no input control on that machine - not keyboard or mouse - even when I had ended the Tv session. Ultraview is a remote administration tool which can also fall into the category of spyware. As mentioned in the introduction, UltraViewer is a legitimate application that offers remote access/control functionalities for single/multiple devices, file sharing, chatting, etc. In my case, I use Tv as a mere lazy convenience to access a machine in another room of my house so, after discovering this issue, I just decided to see if there was anything wrong on the remote machine itself. I tried checking through multiple options, particularly 'disable remote input', and nothing worked.

I just ran into a similar problem a few minutes ago: I could interact with the remote machine with my mouse, but all keyboard input remained inactive (this is the first time I have experienced this issue with Teamviewer). This is actually more of a response to this question, but I thought would still be relevant here.

Ultraviewer remote control