@Nada Thank you so much for posting your solution!! This is still an issue into version CC 2019. Adobe needs to fix this! I updated software, tried every trick in the book, even uninstalled and reinstalled. Not sure if this is affected by fonts other than Avenir. FYI, if you just deselect ‘Include embeddable fonts’ on the HTML & CSS tab it works. It is possible that there is a fail built into the Avenir font to protect copyright. It’s always best practice to NOT embed fonts unless the client/you own the license to embed it.