Cant Save Options

I was happy to find one plugin finally that enables WordPress website owners to do this Progressive Web App smoothly.

But this plugin isnt working. The fonts drop down isnt showing any fonts.
And when I try to upload images for logo and cover, the path isnt getting shown. And moreover none of the three save buttons in the settings of this plugin isnt working.

Inter phase looks very neat and clean, so kindly fix these bugs. The feedback email form you have in the backend is also not working.