Your license agreement appears to need a little bit of work, e.g., it does not include the social media attribution that it claims it does and your support staff think it does.
More worryingly you promote the service as being usable on an ebook cover and then bar use of the image on social media without embossing a copyright to the photographer, but an ebook cover is not copyright to the photographer as her image is only one part of the cover, at the very least a title and author name will be added. So adding copyright photographer / Adobe Stock would be legally incorrect as the copyright for the ebook cover does not reside in the Adobe Stock photographer, only her image. Had I realised how restrictive you were going to be I would have bought the exact same image from Dreamtime or someone else who sells the image without this ill thought-out social media restriction. Once that ebook appears on a site like Amazon it can be placed via their servers on social media by an Amazon affiliate marketer. Every time the Amazon link to the book is placed on Facebook that service will automatically show the ebook cover. There is no way for the publisher to stop this happening.
As your regulations currently stand they cannot be obeyed and used on the ebook cover that you claimed was permissible. I feel that I have been sold the image licence under false pretences, but hope that it is just that Adobe Stock is new to this game and has not thought through how images are used in the ebook industry. Please clarify whether I can use this image on a ebook or not. If the social media restriction is interpreted as in the licensing agreement the answer is not. If you want ebook covers to be an allowable use please inform me when and how the licensing agreement will be changed.
I couldn't hang around for Adobe Stock to learn how to write licensing agreements or how designers use stock photographer. I hope they learn, but I bought the self-same image I got from Adobe Stock off Dreamstime and used it instead. Adobe Stock need to change their practices before I will deal with them again.