Problems with exporting webp

Hello everyone!
I’m working with Aseprite on some animations backgrounds and I absolutely love it, but when I try to export them in webp, after I select the output format and all the options and press “export” the program simply doesn’t do anything. It just keeps working but doesn’t start any export process. It works with every other format.

I am using version 1.2.25 on Mac. I use an old Macbook pro with MacOs Sierra 10.12.6