I've had this across two different laptops while using Windows 10, so I thought it was an OS issue.

There are threads about it on the Windows support forums, for example:
https://answers.microsoft.com/en-us/windows/forum/all/windows-10-touch-keyboard-icon-not-working/87b1ea80-5a04-4ffa-b52e-f295bac1a412

so maybe you'd get a better solution there. The GUI seems to overlay a keyboard on the screen but it's invisible & inactive.

that's not my case here, services are all enabled in my case

https://answers.microsoft.com/en-us/surface/forum/all/touch-keyboard-is-invisible/ee8aeb24-d902-4eb6-a4b0-3dcbb6e9bc95

this link is describing my problem but nobody seems to have a solution

I'm trying the scaling for blurry apps as the last comment suggested and we'll see how it goes

I tried the scaling thing but didn't work either

can you tell me how you fixed it in your laptops?

According to this thread which you've probably already seen, restarting Windows Explorer via Task Manager might help:

https://answers.microsoft.com/en-us/windows/forum/all/touch-keyboard-not-working-at-all/16bf4274-6266-4126-ad00-742c726be9d2

I can't replicate the frozen keyboard yet, so if you can try this and report back in that thread it might help others.

I wasn't using the touch keyboard enough for me to look into the issue and it's not easily replicatable, so I just ignored it and did a reboot to get it back to normal.

I'll experiment with the touch keyboard over the next few days and report back if a I find a quick fix. But I am fairly certain it's a Windows issue.

We use the Latitude 5285 2-in-1 in our environment and we have the same issue consistently. We set our Group Policy to reboot them every night but that is just a temporary workaround. We haven't had the time to attempt to replicate the problem.