No ring notification / how many phones can be connected

Hi, We purchased a ring doorbell just over a month ago and have a few things we are having issues with. Sometimes the notification for movement will come through but when someone rings the doorbell it will not ring, how can we fix this? Even though there is a strong wifi connection, sometimes it also has an extremely long delay. Also, we have a number of mobiles phones linked to one doorbell, will this affect its performance? Thank you so much in advance for your assistance with this.