When page loads the map doesn’t show all the markers. They appear only when (and IF) I interact with the map (zooming in or zooming out).
This is a problem that all users have, not only me, mostly from mobile.
You can see the difference in attached screenshot and you can see the map here http://www.sosdogtrainer.com
I don't need this plugin if it doesn't work and I'll ask a refund
I load your map on my android mobile and I checked all 18 locations are shown on google maps without any issue where 4 and 3 locations are the load on clusters. You can also check Guide Tutorial on this link https://wpgmp.flippercode.com/docs/how-to-display-map-according-to-specific-screen-size/
we are sorry for your all inconvinience you had, I am on leave till 25 Jan, if you are not satisfied with the product you can request a refund.