icloud photos not uploading

I have 200 GB of iCloud space - My photos have not uploaded on the cloud for over a month. Why is this? I can see my last upload was yesterday but still my photos have not been uploaded. I get a warning asking me to connect to Wifi so the back-up can begin...I'm always on the same Wifi.

If i go to Settings > iCloud > Photos > it says "200 items to upload - 2,2240 items to download" - - - nothing is uploading and nor is anything downloading.

iPhotos on my Mac has the latest photo dated the 16th of May 2015 - This is some time ago now. I would like me all my latest photos on my Mac and iPhone.

Can you please help me fix this issue.

Thank you