Fonts: Encrypted fonts are used. Not every shop supports encrypted fonts.

Hi everyone,
I am working on client project (Books epub Creation). When I export book as Epub Fixed Layout and send to my client. He tell me to solve this error " Fonts: Encrypted fonts are used. Not every shop supports encrypted fonts.". 

I have books in 20 languages and each book has different font.
Anyone please help me how to solve this issue. I search a lot and watch videos but unable to solve this issue.
I shall be very thankful to you.
Regards Yasir Ali