In this case we have several mac computer systems that sync photos to an iCloud account. An iPhone is the device used primarily to take pictures and sync to iCloud. The problem is the iPhone will not sync new pictures to the cloud.
This problem can be caused by a couple factors. The most common mistake is not having all the devices signed into the same iCloud account. Make sure that is done. Another factor is the iPhone operating in low power mode, (lpm). If the iPhone is operating in lpm is will pause syncing until the battery is charged.
An easy way to find out if the device is in lpm is to open the Photos app on the iPhone, scroll to the bottom and read the status lines. If it reads “Paused…low power mode,” then plug it in and recharge. By plugging the device in the syncing may start on its own.