Your client always has a client profile (the one you manage) and a personal profile (the one the client manages). These two are seperated from each other in the sense that updating the one will not automatically update the other. This is because you might not want the client to be able to change the address or other data you have of them.
In regard to adding a photo it works the same way, you might have regulations for what the picture needs to look like, while the client itself wants to put up a different photo on their profile.
You will always need to add a photo of the client yourself in the client's profile, for it to show up on the check-in screen.
Please note that if you connect a client to your portal that had already been using Virtuagym and added a picture before the connection was made, that picture will be transferred to the client's profile. It also works the other way around: if you add a photo to the client's profile before they activate their personal profile, the photo will show up on their personal page.