Fillet Curve command suddenly stopped working

I’m not sure what the issue is but the command suddenly stopped working on my version of Rhino. Even when I open up a new file and draw nothing but 2 simple lines, the curves won’t fillet.

It prompts me to select the first and second curve, but it doesn’t actually do anything. The lines are coplanar because they can be extended and trimmed to one another but for some odd reason the fillet command has simply stopped working.

Any help with this?

So it is working, it may be that your fillet amount is too large for the lines. Without actually seeing the file or at least a screen shot it is hard to give a lot of help.