Cura 4.13.4 connects but won't show temperatures

I’ve finally got my printer to work again using Cura 3.6.40.

Now I’m trying to use it with CuraLE 4.14.4.

It happily imports and slices a test file, and appears to connect to the printer - it says it’s connected, and Print to USB is available to click.

I click that, BUT… the hot end and bed temperatures only show 0 and 1 degree respectively - it’s not reading the actual temperatures, and not apparently heating anything.

Any suggestions for what the issue is, and how to fix it?

PS.

Switching the printer off and on again seems to have fixed things.