When someone shares desktop on Skype (Lync) the image is too small

[Intohouse]

When someone is sharing their desktop over Skype for business to my Windows 10 Surface Pro 4 the image is too small and I am unable to expand.

I have tried the 'fit to window' and 'actual size' as well as 'hiding the conversation panel', but the image is still small.

I'm assuming someone has solved this issue already...

Thanks