webp version for all image size not generated

Thanks for the great plugin

I registered a new image size named “max370” where
I wanted width to be 370 max and height auto

so following code has been used
add_image_size( 'max370', 370, 9999 );

so this is the image path ->
https://www.raadballi.com/wp-content/uploads/2019/06/best-resort-near-dharamshala-test-370×183.jpg

but no webp version exists for this

I expected
https://www.raadballi.com/wp-content/uploads/2019/06/best-resort-near-dharamshala-test-370×183.webp to be the webp version but I am getting 404 for this image size

This issue is not just for this cuztom size but for all the images sizes

actually webp version is being generated only for the full image size and no other size

I have purchased 30000 credits only for this functionality but its not working

can you please look into this

thanks in advance