Hi, could you open an issue at https://github.com/jscher2000/Save-webP-as-extension/issues or send me an email at jscher2000@outlook.com for personal assistance? Until then, if the menu item is no longer appearing on the right-click context menu, you might want to remove and reinstall it, and if you notice a problem in private windows (Ctrl+Shift+P or "Never Remember History") make sure it is enabled for private windows when you reinstall.

(Update: version 1.5.1 pops up a little panel with some more options when the script is denied permission to read the page. Previously that just caused silent failure.)